Drag guides from ruler in exact pixel / point units

When I drag a guide from the ruler in Keynote 7, the guide will not snap to specific integer 'point' position. I notice that the guide can vary significantly in position while ostensibly being located at the same point!

This is perhaps the perfect example of something NOT being a "guide" (i.e. instead being in an undetermined, uncontrollable position).

Is this simply another of the increasing number of bugs Apple is lazily including in its software, or is there an esoteric keyboard shortcut that forces dragged guides to 'snap' to their nearest point position?

I do not find the 'percentage' figure (to two decimal places, no less!!) at all useful and would rather it could be completely disabled.

To be clear, I am at present unable to accurately position a vertical guide at 500 points position on my slide. Apple's crippled Keynote 7 only allows me to position it roughly in this position — indeed, zooming in I can position multiple guides in different locations that all claim to be at the 500 point position!

Brilliant work, Apple.