Persimmon reservation fee

Hi,

Myself and my girlfriend have just exchanged on a Persimmon home which we are due to complete in September.

Something I've asked about is the initial reservation fee of £500 that we put down a few months back, where does this go?

I've asked about this but don't understand, they says it comes off your final bill.

We have a 75% Mortgage and a 25% deposit of the house price and £2300 worth of finishing touches.

So does the £500 reservation fee come off the finishing touches?

Thanks,

Malcolm