First, weigh the bud to see if it is weighed up. I have met one too many people who said, "my bag is underweighed" but once you get it on the scale, oh, what do you know, it IS the right weight. Don't go by looks, go by what the scale tells you.

If it's under a gram, either give it back and tell him to fuck off, or smoke it and just give him $10. I mean, he could be trying to rip you off.