I can make A room ?

I'll show you two sentences and please help me point out
which is the correct one.

A : I have a full plate next weekend,
but I can make room on the weekend after.
B : I have a full plate next weekend,
but I can make 'a' room on the weekend after.

The difference between the two is the existence of 'a' bewteen
'make' and 'room'.

As far as I know, 'a room' referes to a part of the inside of a bulding
while 'room', when no articles attached, means space available for something.

In the context, what is proper, I think, is 'space', not building-related stuff,
therefore, I believe that sentence A is correct and B is not.

Would you please let me know if my guess is right?
Thank you.