In Adobe InDesign (don't know how it is in other adobe softwares) it's a bit more complicated actually BECAUSE OF the accuracy of InDesign's interpretation of decimals.
To test Evan's values I made a simple experiment:
When you set the baseline grid increment (edit > preferences > grids > baseline grid) to the value of 1 pt and then on the page you will create a rectangle snapped to the two nearest baseline grid lines... you will end up with a rectangle of a height of exactly 0.353 mm.
Because InDesign apparently rounds the values of 1 point (0.352777778 mm) to the three decimal places (therefore 0.353 mm).
- IN THEORY: 1 PostScript point = 0.352777778 mm
- IN INDESIGN: 1 PostScript point = 0.353 mm
- DIFFERENCE: 0.353 mm - 0.352777778 mm = 0.000222222 mm
It seems not important, but becomes a problem, when you will need to multiply the values for some reasons. Let's say you have 250 baseline grid lines incrementing by 1 pt, and you need to create a rectangle of exactly the height of those 250 lines.
- IN THEORY: 250 * 0.352777778 mm = 88.1944445 mm
- IN INDESIGN: 250 * 0.353 mm = 88.25 mm
- DIFFERENCE: 88.25 mm - 88.1944445 mm = 0.0555555 mm
So the seemingly negligible INDESIGN/THEORY difference on the level of 1 point unit interpretation (0.353 mm - 0.352777778 mm = 0.000222222 mm) becomes "magically" more important after multiplication (88.25 mm - 88.1944445 mm = 0.0555555 mm)
Hope it helps! :)
PS: Or maybe We can just set the InDesign's default accuracy to higher values then three decimal places? If so all that I have written above is bullshit. But I don't know if such accuracy setting is somewhere available in InDesign. Maybe someone know?