Presumably if the tenant is not happy with your pro-rated value option, they can file against you at the Landlord and Tenant Board or in Small Claims Court. You are the best judge of what degree the property and you benefit from those items remaining behind. If may be a difficult case for the tenant to prove, given that this is a sort of retroactive claim for reimbursement, and there is no explicit agreement with you, nor is there likely to be any correspondence speaking to the matter.