The 0.19" outline is intended for trimming the already mounted print for placement in a frame. It's just a convenience thing that saves some time.
When actually gluing down the print, just allow a generous amount of extra canvas that will go past the edge of the Gator and leave the 0.19" outline marks mounted on the gator, The purpose of that is to shield glue from being picked up onto the face of print, about 1/8" overhang is the minimum that does that properly. If you get glue on the face of the print, wipe if off IMMEDIATELY with moist paper towel.
Just after the print is glued down, trim off the excess canvas by running a utility knife along the edge of the gator, with the print face up. Be careful not to lift the knife too far and gouge the surface of the print. The purpose of this just-after-mounting trim is to get rid of dry canvas which would cause ripple at the edge of the glued, wet canvas during drying. Never lay the print face down on the work table because it will probably get contaminated with glue.
PS There are dozens of lengthy posts about gluing canvas on this forum!