Need to see what the rpm scale is on the bottom of the sheet, and the HP scale on the right?

The upper most curve looks like it’s at about 440ft/lbs where it ends.
What rpm is that at?(or is the scale “speed”)

68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123
Dealer for Comp Cams/Indy Heads