I had a very similar experience with this guy. I specifically texted him the amount and asked if that was okay so we were both on the same page as far as donation. He then tried to short me by 100. He found a little more cash in his wallet but i left with him still owing me money and saying he would take care of it next time. Not too surprising i have not heard from him since, which is a shame because he seemed to be a super nice guy aside from his not completely taking care of agreed upon donations.