Remove plastic bag logo
Try different solvents on the bag to see what removes the ink. The try an effective solvent on an inconspicuous bit of upholstery to see if it damages it.

You might need to make a paste of the solvent and an absorbent material, such as diatomaceous earth (used in swimming pool filters), to keep the solvent in place and to wick away the stain. 

Look online for other tips on leather cleaning, e.g. Bob Vila's site.