Stats and modifiers in Last Epoch can exist in 3 main categories: added, increased, and more. The category a modifier belongs to determines which step it will be used at in calculations. Not all stats will have modifiers for each category in practice.
(5 + 2 + 3) = 10
First, all added sources of the stat are totaled together.
(1 + 0.05 + 0.3 + 0.1) = 1.45
Second, all increased sources of the stat are totaled together. Increased values are percentages, so they are converted to decimal numbers and an additional 1 is added. Reduced sources are subtracted from this same total.
(10 x 1.45) = 14.5
Third, the total of the added sources is multiplied by the total of the increased sources.
14.5 x (1 + 0.05) x (1 + 0.3) x (1 + 0.1) = 21.77
Finally, the product of the added and increased sources is multiplied by each more source. More values are also percentages, so 1 is added each time. Less sources are also applied here as values subtracted from 1.
Note that the more sources are not added together first, which would result in a different number. If the more values in this example were totaled first, the final result would be 21.03, not 21.77.