That is the kind of mark left when the vase was snapped off the pontil rod, which is used by the glassmaker to hold the piece while it is being worked. Sometimes they can be quite rough to the touch, sometimes they are a bit smoothed by reheating. Known as a snapped off pontil mark.
If you see a concave polished recess in the same position then the mark has been ground and polished away (called polished pontil mark).
John