I agree, get some info from Robertson on it and do some reading.
It sounds a little fishy to me but I'm sure it's fine.
Does it have the VG's on it? I fly a 414 with the VG kit that increases gross weight but I'm not a fan because there was no increase in the horse power of the engines. So with that extra weight and the same factory engines it's going to be ugly if you lose an engine.
Keep looking for a pilot out there that flies this same plane as you and see what they have to say about the performance numbers.
Good luck.