Notes moving off grid

I do not know If anyone else has had this problem or is old hat .

I Have a fast i7 computer and noticed that when quantising some notes and going back later ,the notes move maybe a square forward of the grid.
Have i got to do something with something in preferences by raising or lowering milliseconds in the midi section.I only have a vaue idea.
I am not sure exactly what i have to do.
If anyone knows what i mean i would appreciate some help in what exactly i have to do.

All the best


Make sure the Bars & Beats ruler is selected.

Is the iQuantize switched off or set to 100%?