GESI how to get Order type for sheets

Hi there.

I am trying to set up a sheet with GESI and am stuck on getting current buy price on an item using =markets_region_orders but i can’t for the life of me figure out what the order_type choices are (see screenshot posted below).

Typing in sell or buy does not work and i can’t seem to find a list of options for the various functions and what the choices could be.

Is anyone able to assist?
Thanks in advance,
Fly Safe - o7