I Read the above - you didn't really get your answer did you. = )
In most cases if wants the guiding scope info. For a guide scope (see their specs) often 50mm and maybe 240mm.
With a OAG you need to enter your primary scopes specs.
When I use a OAG. (which is most of the time). When I'm setting up my 80mm. I enter the focal length for the scope (480mm) in the stellarvue specs. It's aperture is 80mm. (size of the objective).
If I use a field flattener (usually) it's the 480mm x .8 (.08 FF) so that makes it a 384mm aperture 80mm.
When I use my 6" APO it has a .75 FF. So it's a 1216mm scope. AP is 152mm. (6") with the FF it's 1216 x .75 so I enter 912mm FL and 152mm AP. (aperture). size of the primary for light gathering.
If will often ask for pixel size and often the width and height of the guide cameras sensor. Find that in the specs for your camera.
So to answer your question - enter the FL and objective mm of the primary telescope which is (WITH A OAG) also your guide scope.
OAG's are great - I have 3. I like to leave them on each scope as a single unit to swap out. The hardest part is adjusting the depth of the prism into the FOV and not allow it to cast it's shadow on the primary cameras sensor. If you pull it out to far you will get distorted stars on the fringe of the projected image. So better to get in INTO the projection area to get a nice sharp star.... but not so far in that it leaves a shadow on the primary image. A little balance is called for. Then the distance of the guide camera has to be the same distance as the main camera... because they both need to be set to focus at the SAME POINT from the primary scopes focuser. Focus the telescope and primary camera first. Once in focus slide the guide camera up and down (to change distance) while looping the view and find the spacing with the best focus. Lock it down with the set screw(s) and then when you focus the primary image the guide image will also be in focus. Sometimes this will take extra extension tubes to find the proper focus distance. Once set - forget about it!
I never fear asking a dumb question because after someone answers it, I'm not as dumb as before I asked! = )
Couple pics attached if two different scopes with my OAG's.
AP Mach1 / CP4 APCC & PEMpro.
EXP SCI - ED152cf APO - Celestron 11" RASA - Stellarvue 80mm
Baader F2 HS NB filters, Lodestar X2 guide camera / OAG - ZWO 290mm mini
ZWO ASI1600MM Pro / ASI174M (solar) / ASI094MC
NEXDome, CLoudwatcher, AVX mount/ASIair and Stellarmate