Grinding direction

There is a suggestion that the glass being ground should be passed along the in the direction opposing the spin of the grinding bit.

The grinder bit rotates in a clockwise direction as you look down on it.  This means the grinding surface is moving toward the left.  The recommendation is that you will get more efficient grinding by passing the glass to the right, against the rotating direction of the bit.

This is more theoretical than practical. In practice, the bit is spinning so rapidly that only a minor difference, if any, can be perceived.  Without a noticeable difference, there is no reason to be concerned. Move the glass you are grinding in the directions that you find convenient.  You will find a little more resistance when you move the glass from left to right, rather than the other way.

You are much more likely to damage the bit and grinder motor by excessive pressure against the bit than by any directional movement.