throughput very low in controller

Hello   I want ask expert fortinet for this problem !!   1)     i configure fortiAP221E  in a forticloud .. we test the throughput  for this access point, we see the throughput w is  good     2)    while, we try to configure this FortiAP 221E( same access point )  on controlle,   then it gives us that the throughput  is very low  !!!!???   SO  why the throughput  is strong for forticloud  ,  then the throughput is very low for the same access point  is very low 1Mbits   for  controller  !!????   what is the reason  !!!!    I wait a repy from expert fortinet  to answer me for this problem !!   best regards