The property developer decided to forfeit the 25% deposit in return for not pursuing him for the 75% balance.
I think that it should have read :
"Mr A decided to forfeit the 25% deposit in return for [the property developer} not pursuing him [Mr A] for the 75% balance".
Under a normal contract for the sale of a property a failure to "complete" by either party gives the other party the right for specific performance; rescind the contract etc. but not recovery of the deposit if the person placing the deposit (ie the purchaser) fails to complete.
In the present case the buyer, Mr A having failed to proceed with the purchase gives, prima facie, the right to the developer to force Mr A to proceed. However, it would seem that the developer decided to simply not proceed (I would suggest already having the right to retain the deposit). If this is correct then the developer received no "capital sum" in return for a forfeiture of his rights and thus
s22(1)(c) would not apply; to this extent I think the quote provided by DonkeyAccountant (my or his version) is perhaps misleading.
However, we do not of course have full details of the precise terms of the contract between the two parties.