Issue with league prior recording 220-300 fps while recording 20-27 while using any render option maintains at 60 fps when using original any recommendations ?

Hey guys, Having troubles using the recorder, before recording my frame rate hovers anywhere between 220-300 fps however after starting a recording in 1080p-240p in any format however if I use original size i drop to around 150 fps (all in 60 fps framerate recordings) any idea what may cause this is...