Often small businesses will use a 10.0.0.0/8, 192.168.0.0 /16 etc as they don't know what to fill in.
====SIDE A====
object network REAL-LOCAL-A-NET
subnet 192.168.1.0 255.255.255.0
object network MAPPED-LOCAL-A-NET
subnet 172.18.19.0 255.255.255.0
object network MAPPED-REMOTE-B-NET
subnet 172.18.20.0 255.255.255.0
nat (inside,outside) source static REAL-LOCAL-A-NET MAPPED-LOCAL-A-NET destination static MAPPED-REMOTE-B-NET MAPPED-REMOTE-B-NET
access-list VPN-ACL permit ip object MAPPED-LOCAL-A-NET object MAPPED-REMOTE-B-NET
===SIDE B====
object network REAL-LOCAL-B-NET
subnet 192.168.1.0 255.255.255.0
object network MAPPED-LOCAL-B-NET
subnet 172.18.20.0 255.255.255.0
object network MAPPED-REMOTE-A-NET
subnet 172.18.19.0 255.255.255.0
nat (inside,outside) source static REAL-LOCAL-B-NET MAPPED-LOCAL-B-NET destination static MAPPED-REMOTE-A-NET MAPPED-REMOTE-A-NET
