You can borrow 6 bits. Which would create a 255.255.255.252 subnet mask, but this subnet only contains 2 usable IP addresses.
7 bits would be 255.255.255.254, but that subnet is too small to have any use in the real world.
254
16
The maximum number of hosts per class B network is 65536.
Each network supports a maximum of 16,777,214 (2 24 -2) hosts per network
Since this is a class B network you have borrowed 8 bits for subnets. This leaves 8 bits left (1 octet) for clients/workstations. That gives you a maximum of 254 clients per subnet.
class A supports maximum number of hosts. | | | | | <------network------><--------------------------------hosts------------------------------------>
The maximum number of host bits that can be borrowed from a class A address is 22 (technically you could borrow 23 but the resulting network would be useless). A class A address uses 8 bits for its network address and 24 bits for its host addresses. Class A uses a subnet mask of 255.0.0.0 You can only borrow 22 bits (instead of 24) because a valid network requires 4 addresses: A network address, two host addresses and a broadcast address. These networks would result in 30 bits used for the network address and 2 bits used for the host addresses. These networks use a subnet mask of 255.255.255.252
14
100
4
255
The scale is the maximum of the total number line and is used to create the base of the question and number line.