Im just began seeing this problem..when im above 18000 ft my alt is set to 29.92 but RC is giving me readings in the 30.xx what could be causing this? Yes I do use the control on the plane not the B key

ATC always reports surface pressure to be used below transition altitudes. It is an advance notice.

 

When RC gives you as an example a descent that may take you below the transition altitude, it will give you surface pressure as read by fsuipc from FS. That allows you to set your altimeter as you go through the TA limit in advance.