Too many Floors

Chef and Chefina are residing in a hotel. There are $10$ floors in the hotel and each floor consists of $10$ rooms. - Floor $1$ consists of room numbers $1$ to $10$. - Floor $2$ consists of room numbers $11$ to $20$. $\ldots$ - Floor $i$ consists of room numbers $10 \cdot (i-1) + 1$ to $10 \cdot i$. You know that Chef's room number is $X$ while Chefina's Room number is $Y$. If Chef starts f