currently you only can see available contracts for shops and restaurants if you click on an already laid out shop region. So, You may be lucky and the needed space is what you defined as shop region or you’ve too little space for a given contract or too much (waste of space).
I suggest to make the available contracts visible in the contract overview. Benefit is that you can make the shop region as big as required without wasting too much space and you know how the shop region has to be laid out (sometimes rectangular is better than square). And it would be more realistic