Cheers, I knew the top parts and then saw the edit, will have to look at that, thanksIt all depends on what you accept in the transfer. A small break down:
Transfer Fee: This is the amount you get up front.
Monthly Installment: You will get the amount proposed over the course of the time proposed (for example: you agree to get 1.2m over 12 months, you will get 100k per month.)
Other clauses: as indicated, but could be: Money after amount of appearances (domestic or international) among others.
The trickier part is this: When you have offered your player a contract, he may have asked for a sell on fee. In practice this means the following. You agree in player X his contract that he gets a 10% sell on fee. Imagine that you sell player X for £10M. This means that he will get £1M from the transfer fee. Try and avoid those if you can .
One more issue might be the following: your player has a release clause of, for example, £20M. A team paying that money might have offered you that money over a 48 month period (monthly installment). This means the offer will still be accepted, but the money will only come in slowly. You will get 5M after each year in this case.
EDIT: I thought of one more obvious thing. Check your finance summary. There you will see how many % of the transfer revenue is made available by the board. This might be less than 100%.
That is all I can think of. I hope it helped and if you knew this, I'm sorry