How many lessons does this student have left? Seven states, and the rule that moved each lesson

Two fields, both off the package the family bought. The label is for your own recognition only. This page asks for no student's name, stores nothing, and sends nothing you type anywhere, because a private student is often a child and a record about a child is a record about a child wherever it is kept. What the page does send is four aggregate counts about itself and the host name of the site you arrived from, set out in full at the foot of the page.

Five rules and two week counts, all of them yours. Three of the rules are boundaries between the seven states on their own: change the make-up rule, the cap or the no-show rule, and lessons move between the owed, the unscheduled and the two forfeited rows while every figure you typed stays exactly as typed. One thing stops all three: the column each one reads. The make-up rule and the cap read the cancellations that carried your notice period of warning, the no-show rule reads the ones that did not, and a rule whose column is empty moves no lesson at all, which the rule cells in the table say row by row when it happens - so a register with no cancellation logged in it moves nothing whatever you set these three to. The expiry window and the two week counts reach the lapsed row only together: set a window, count weeks past it, and every lesson still owed and every lesson still unscheduled lapses with the package. Two separate things can stop a week count moving a lesson. A window set to nothing switches expiry off for good, so no count of weeks moves a single lesson after that. And a package whose weeks elapsed have not yet run past its window loses nothing to expiry whatever the window is, which is where the shipped example sits: one more holiday break on the example widens its window and moves no lesson, because the weeks elapsed had not reached the old window either. The notice period is the one rule here that moves no lesson by itself: it decides which of the two cancellation columns in section C a cancellation belongs in, and you type that split yourself. The page asserts no rule of its own and recommends none.

Two running totals a teacher keeps, and two splits of them that many teachers do not. Each split has its own line beside it saying what leaving it at nothing does to the figures: the first leaves your balance and your forfeited and lapsed rows exactly as they were and moves two splits inside them, one of which is a figure at the top of this page; the second moves the balance itself, which is the one your policy treats differently. The page says which is which instead of pretending they are alike.

If your register keeps one running total of lessons used and does not record which of them were make-ups, leave this at 0. The balance, both forfeited rows and the lapsed row are the same number either way; only the split between lessons taught at their scheduled time and lessons taught as a make-up, and the split between make-ups still owed and lessons unscheduled, moves.

If you kept one cancellations count and did not record how much warning each one came with, enter 0 here. The page then prints, beside the no-notice row, how many lessons one more cancellation in this column would change your balance by under your own rules, so you can see the size of the split before you make it; the page will not make it for you, because it is the one thing your policy treats differently.

One row per state, with the count of lessons in it and, in a cell of its own, the rule that put it there. The total row is the package you typed, exactly, in every state of every sweep this page's test suite runs. Nothing here is a figure in money and no row is an opinion about your terms.

This arithmetic written out for anything that reads this page instead of looking at it: api.json beside this page carries every input, every output, the formula line by line, this worked example, and a list of what the calculation deliberately leaves out.

The balance shown is lessons bought less lessons taken less make-ups used, under the rules you set on this page, with the working shown.

Your lessons-taken total already carries the make-ups you have given inside it, so no lesson is counted twice here; the three rows that follow are what the rules you set take out of the package - the no-notice rule, the make-up rule with its cap, and expiry.