I wouldn't trust any pimple faced employee cutting my wood. I hate that. I've been using power tools for 20 years. It's an insult for this teenager to tell me that I'm not qualified to operate their saw. Not to mention "their" saw is so far out of calibration it's not funny.
HD, Lowes , Ect, saws are not very pricise. They cut wood mostly for ppl who nned to get it cut so they can fit it in thier cars. Thay are they same ppl who push those big carts full of flowers and potting soil, 1/2 dozen cinder blocks, and 6 sheets of awful wood simulated paneling right into the saws guide bars, throwing it out of whack. Your best bet is to buy a circular saw, a straight edge and a couple of clamps. Last resort, drive up to some job site and give some contracter a case of beer to cut what you need.
And I thought you were excited about a new box you just got.. Go figure.