In previous version of Blender, the measurement units fields were in pixels, so that if you image was 2048 wide, and you wanted to place a UV exactly 10 pixels in from the right, you would enter ‘2038’ in the X field.
In 2.8, measurements are now a percentage express as 1 = 100%.
This means to place a vertex exactly 10 pixels in from the right, you need to do the following:
1 / 2048 x 2038.
That is long-winded and may also give you a rounded number in some situations, when a precise pixel can sometimes be very important.
Is there a way to switch it back to pixel measurements?