What the three numbers do
The deposit is your percentage of the price, but never less than your minimum and never more than the price itself. The minimum is what protects a small piece: a percentage of a small price is too little to hold a day, so the floor takes over. On a big piece the percentage wins, so the deposit grows with the work.
This is worked out exactly as Chairtime works out the deposit on a quote, so the figure here is the figure a client would be asked for.
Pieces over several sittings
The price is split evenly across the sittings, with any odd pennies on the first, so the sittings always add back up to the price. The deposit is taken for the first sitting and comes off it. If the deposit is bigger than an even share, the first sitting is made as big as the deposit and the others share what is left, so no sitting is ever paid for twice.
What the no-show figure means
A no-show costs you the whole slot: the time you held, the work you turned away for it, and often the drawing. The figure counts each no-show at the price of the piece, or of its first sitting, which is what the empty chair was worth. The deposit is the part of that you keep. It will not stop every no-show, but a client who has paid something is far more likely to turn up, and far more likely to tell you when they cannot.
For the amounts most artists use, and how to word the cancellation rules around them, read how much a tattoo deposit should be.