Legal Question in Landlord & Tenant Law in Illinois

First, a "full" and "twin" are really the same size for all intents and purposes. But more importantly, the landlord says "if applicable" so there must be something in the lease that makes his obligation less than absolute. You should have an attorney review the lease.

While I am an active member of the Illinois Bar, this Answer is intended solely as a courtesy to the Questioner based on an incomplete set of facts, so that the Questioner can be encouraged to obtain proper and complete legal advice based on all of the necessary facts.

This is not meant as a definitive answer but a general narrative to assist you in heading in the right direction. Any law cited or referred to specifically or generally may or may not apply to a specific set of facts. We nevertheless hope this is of some help to you.