The AIM-120C rockets are supposed to be showing as 3, but only 2 are showing.
It’s a known issue: ( Community Bug Reporting System ).
In the future you can bug report issues here (just search a bit first so that you don’t report something that is already reported and known about): (Gaijin.net // Issues)
A guide on how to report bugs can be found here: ([Navigation] Technical Knowledge Base | War Thunder Wiki)