subnetting vs supernetting

Masked bit	mask value	Number of subnets	Number of  hosts/subnets	Approximate number of host/subnets
/20	255.255.240.0	5c	4096	4000
/21	255.255.248.0	4c	2048	2000
/22	255.255.252.0	3c	1024	1000
/23	255.255.254.0	2c	512	500
/24	255.255.255.0	1c	256	250
/25	255..255.255.128	½c	128	125
/26	255.255..255..192	¼c	64	60
/27	255.255.255.224	1/8 c	32	30
/28	255.255.255.240	1/16 c	16	15