Should the bike be level and upright when checking brake fluid level in the master cylinders? Owners manual doesn't say. I think yes but not sure on this one. 2010 EGC
A touch low as you say is probably ok. Personally, I would only fill it full if I had brand new brake pads. As the pads wear the fluid level will go down. If you fill the master cylinder with used/worn brake pads then it will be overfull and quite possibly overflow when you depress the caliper pistons for new pads.