Why am I getting only ip address whereas I configured Pool ( 10.50.1.1 - 10.50.1.100)

Dear All, 

I have configured L2tpvpn in my organization with fortinet firewall 1200D and able to connect my gateway but why am I getting only one ip address in that pool whereas I configured Pool like - (10.50.1.1 - 10.50.1.100) and getting ip in this pool 10.50.1.85

Please share your kind respose .

Regards,

Umesh