Right thats it! I give up! I have just spent over an hour trying to figure this out.
I even almost emailed the hotels customer service department, but apparently it can take up to 35 days to get a response (plus; I would look like a crazy person)

So.. I am just going to take a stab in the dark and guess that the number of rooms on the 4th floor is 24.

I might still ring round some hotel receptions tomorrow just because I dont think im going to be able to wait 7 days 😄