https://ux.stackexchange.com/questions/13795/is-there-a-standard-to-left-justify-text-and-right-justify-numeric-values
简而言之，这样可以对齐数位，易于肉眼比较大小
English text is usually left-aligned. Numbers are normally aligned so that the various places (unit, tens, etc.) are in columns.
If the numbers are integers, this just means right-aligning the numbers.
If they have decimal fractions, then the decimal places should be aligned, with the units digits all in a vertical line.
This makes it easy to compare the numbers' magnitudes.
Mac OS X gets this wrong in the Finder: File sizes are given in abbreviated form, such as 342kB or 6MB. When reading a file listing, it's hard to spot the 342MB file amongst all the 342kB files.
Numbers should always be right justified if they're to be compared, especially for cash amounts;
this keeps the decimal in the same place if the items are rounded the same and makes arithmetic and comparison easy.
By Ben Brocka
Numbers should be right-aligned only if their fractional parts are a fixed width (for example, cash amounts probably have a decimal point and 2 fractional digits.).
But for example, if your list is 2, 14 and 3½ then the numbers should be aligned on the units digit, not right-aligned.