You need to enter the exact amount stated on the tenancy agreement, e.g. £1,153.84. If you can’t remember this, check your tenancy agreement.
If you can’t find a copy of your tenancy agreement, ask your agent or landlord to provide a copy. Also, ask them to provide a copy of your deposit protection certificate, which will also hold all the information you need. TIP, save a copy of your tenancy agreement and your deposit protection certificate to your document storage facility in tlyfe for easy reference.