Help subnet mask:

24 = 255.255.255.0       HostMin: 192.168.0.1       HostMax: 192.168.0.254       (254 usable IPs)
23 = 255.255.254.0       HostMin: 192.168.0.1       HostMax: 192.168.1.254       (508 usable IPs)
22 = 255.255.252.0       HostMin: 192.168.0.1       HostMax: 192.168.3.254       (1016 usable IPs)
21 = 255.255.248.0       HostMin: 192.168.0.1       HostMax: 192.168.7.254       (2032 usable IPs)
20 = 255.255.240.0       HostMin: 192.168.0.1       HostMax: 192.168.15.254      (4064 usable IPs)

 

https://www.calculator.net/ip-subnet-calculator.html