Thank you for posting to the Fortinet Community Forum.
As per your description your query is regarding how many ports in FGT are mapped to default IP 192.168.1.99
It totally depends on FGT model you are using.
Can you let me know the model you are using.
For some model which has mgmt port then only the mgmt port will have the IP 192.168.1.99
In some model where mgmt port is not available then by default the internal port are kept on hardware switch mode and all the interface will have the same IP 192.168.1.99 since they are working as switch mode.
Please check datasheet regarding the same.
Let us know if this helps.
Salon Raj Joshi