The 5% deposit is an exchange deposit, which is often agreed upon between the parties at the time of the exchange of contracts. However, it is common practice for the contract to state a 10% deposit as the standard amount required upon exchange of contracts in property transactions.

In your case, while you are paying a 5% deposit, the contract may still state 10% because, in the event of a default, the seller has the right to claim the remaining 5% to make up the full 10%. This provides the seller with a form of security. However, as long as both parties have agreed to the 5% deposit, there is usually no issue, but it is important to ensure this is clearly documented and agreed upon in writing.