The cutters are almost aways under size and like you said, you now know the size of your cutter and can make the cut to suit by using you tool geometry in your cam program, or use a G41 /G42 in your code and then you can adjust the cut of your part, sometimes it is just easer to just know you tool diameter, your cutter does seem smaller than normal .0025" lower quality cutters you can expect cutter size variation.