First of all that weight isn't anything, the stack is 300 and the guy right over you accout for most of the weight, the other two people are so far back you have too much leverage, if u actually think you were doing all their weight you are mistaken.
I do 750 lbs of real weight for 10 reps and my calves aren't anything. I'll struggle with 800 for 8, but the calf machine I have at the gym now, I can put on 1,000 and do 20 reps easily because of where the weight stack sits in realation to your shoulders. I could post a pic of me with 100 lb plates pinned to the machine, it may look impressive but its not, its all in relation to the leverage that you get from the particular machine.
Not trying to be an asshole, but its certainly nothing to brag about, and I would laugh at any guy that had 3 guys on the machine, talk about trying to get attention, I know arnold did it, but your not arnold.