Please help, about how many calories in this meal?

I went to the Harvester restaurant and chose one of the healthiest options which was a flame grilled chicken breast burger. On the menu it said there were 480calories. BUT I chose to have it without the mayo, and it came with two large chicken pieces in it, but I only ate the one as it was too large a portion*, So from 480, how many less did I have, how many calories in total? The burger bun was a normal non-seeded bun, similar size to a McDonald's one, with a slice of tomato, lettuce and onion.

*whether the chef made a mistake and put two chicken pieces in I don't know, but I'm guessing that's the standard serving size for the 480 cals