Calibration Sheet

FIG. 1 is a top view of calibration sheet, showing the new design; FIG. 2 is a front view thereof; and, FIG. 3 is a left side view thereof. Broken lines represent portions of the calibration sheet and environment of the claimed design that form no part of the claimed design. The bottom view is omitted because it has no pattern, the rear view is omitted because it is the same as the front view, and the right side view is omitted because it is the same as the left side view.