Send it back. It would bug me everytime I looked at it. Some have observed it is cosmetic. Technically true, but having bought OEM automotive castings, without ultrasonic testing there is no way to see how long and deep the porosity goes. A few years of sliding your miter gage can open up the defect even more and then it will be too late for recovery. For $2000 the top should be near perfect and this one isn't.
Take off a full blade, nope, too long, now take off 1/2 blade, nope, too long, now take off 1/4 blade - How the H--- can it be 1/4" short????