Why do some table saws have a direct and a reverse ruler on the fence?
You have a "reversible" fence.  One set of measurements are for when the fence is on the right side of the blade, and the other set of measurements are for when the fence is on the left side of the blade.

Remove those 2 red knobs on the right side of the fence and remove the bolts/fence.  Now put the bolts through the other side (where the red knobs are) and put the fence on and the knobs.  Remove the fence assembly from the track, move to the other side of the blade, put fence back onto track, now you can measure/cut from the other side of the blade.