Stormcrow is correct we have been down this very argument before. The cut commences at 0.1G.
A mechanical G meter/accelerometer used in Aviation uses 1G as its static reference. Sitting in your chair holding a G meter it would read 1G.
Here is a typical G meter as fitted in a YAK52 sitting on the ground the needle showing 1G.
In cruising flight the aircraft is at 1G as the pilot progressively pushes forward the G decreases towards 0 G. The document states that a reduction of 0.9G. So the G meter would be reading 0.1G that's the needle just above the 0G mark as indicated in the graphic. As the document clearly states ..."i.e. at an accelerometer reading of less than 0.1g" ... or 9/10ths of G worth of Push ! or mathematically 1.0 - 0.9 = 0.1