cardiod pattern mic not good for measuring. It "hears" differently from the sides and back than from the front, and that will skew measurements. Also lots of roll off in the bass (minus about 6 dB by 50 Hz, the manual does not show frequency response any lower, but safely assume the roll off continues at least as strongly as what is shown. Full range, it's reasonably flat from 100 Hz to about 15KHz, but then rolls off sharply (from the front). FR is all over the place from the back, and there's not going to be a location in your room where sound doesn't bounce off walls, floors and/or ceilings and reach the mic from the back (or sides . . .)
In short, not an ideal measurement mic by a long shot . . .