Gas Tank Capacity - Reserve level

[LifeTimeRiches]

OK so I topped off my tank and rode without a refill for 150 miles. I just happened to look in the tank and there is zero gas in there, nothing but a dry tank (I just happened to get lucky and make it home and look in the tank). My fuel lever says RES/PRI/ON. The RES is facing up, PRI is facing to the right (towards the back of the bike), and ON is facing towards the ground. I leave the lever in the ON position always. So here is my question, when am I supposed to turn the switch to RES for the reserve if there is no gas left in the tank. Then book I think says there should be 0.9 gallons for a reserve. I am thinking my petcock is broke and flowing fuel through the reserve line no matter what I place the lever on. Or do you think the lever is on backwards/upside down and when I place it on "ON" its really on reserve and vice-versa. Guess I will have to refill the tank, ride some more while placing the lever on RES and see what happens at 150 mile. Also doesn't 150 miles on a full tank sound a little low?