I think here they are asking how much extra 1’s we can use in the network or how much bits we can borrow from the host to make 1’s.
here the given network id is 255.255.224.0.
and as per the standard the subnet mask of class C is 255.255.255.0
224 = 11100000 and 255 = 11111111
thus as we have 5 bits to be included in the network id .
so from 5 bits we can add 2^5 networks i.e 32 networks.