Thanks for update.
In Maximum Value Guide.
- Local Users - 20
- Local Users Groups - 100
In FG30D Tech Datasheet
- Client-to-Gateway IPSec VPN Tunnels - 250
- Concurrent SSL-VPN Users (Recommeded Max) - 80
- Max Number of FortiTokens - 100
What use of above values if there is Local users limit is 20 max.
20 Local Users is the maximum of locally authenticated users you can have. The reason you can have 100 groups is because you can place non-local (e.g. LDAP) users within this group, or indeed AD groups if using FSSO.
As suggested, look in to external authentication methods such as LDAP.