Someone posted earlier posted that during their(?) DSD they were giving some basic instruction (hand signals, mask clearing, pressure gauge, etc). That's exeactly how my DSD (PADI) went last August in Maui. I went through a brief on-shore lesson on hand signals, how to use the BC, purge the regulator, clear my mask and how to read the pressure guage. All this before getting in the water.
Now, maybe age as something to do with it (Iwas 54 at the time), but on both my dives (max depth 30ft), I did a second tank after the initial DSD, I made sure to check both the SPG and depth gauge often, probably too often, but I wanted to make sure that I had enough air
.. I had the advantage that it was just me and the insructor, but in addition to my own checks of the SPG, he checked often since he didn't want to have me suck the tank dry. His policy was that betwen 1500-1000lbs of air, then surface. My DSD was such a positive experience, that I came back, found a local instructor, and completed my certification last October.
In my opinion, chalk it up to a bad experience, and if you want, find a reputable instructor and get the proper instruction.