Bengaluru is located at 78E longitude, San Francisco at 122W.
Accordingly, flying west from Bengaluru over the Atlantic to San Francisco covers 200 degrees of longitude.
But flying east from Bengaluru over the Pacific to San Francisco covers only 160 degrees of longitude. Clearly, that's a shorter route -- but it's still 8,699 miles.
Thus, whoever drew the map made an incorrect assumption about the routing.
here’s the great circle route. The Distance is within the range of a 777-300ER or 777-200LR. Which Air India operates.
http://www.gcmap.com/mapui?P=sfo-blr&MS=wls&DU=mi