A proportional calculation can produce a fractional dimension even when every input is whole. The fraction is the mathematical result; the rounded value is a practical choice. Showing both prevents a rounded output from being mistaken for the exact proportion.
Nearest uses half up
For an unrounded missing side of 562.5, nearest with half up returns 563. A value of 562.49 returns 562. This rule minimizes the numerical difference, but the unrounded result should remain visible.
Ceiling and floor make direction explicit
Ceiling moves any fractional positive value to the next whole number, so 562.1 becomes 563. Floor moves it to the previous whole number, so 562.9 becomes 562. Neither is universally better; choose the direction required by your numeric constraint.
Copy the rule with the result
A rounded pair is usually close to the source ratio but may not reduce to exactly the same terms. Keep the unrounded side and selected rule beside the copied pair so another person can reproduce the decision. AspectFit calculates numbers; it does not change a file.