Scaled Drawing scales

Can anyone tell me why the list of available scales differs depending on whether you choose Architectural, Metric, or certain units?

Also, how do you populate the list if the scale you want doesn’t show?

i guess because of metric / imperial units systems

Edit : Preferences

Thanks @paul.millet and @mihai.s.

But here’s what I get, depending on what type of units I select:

Seems to be that I only get the full list if I choose mm as the units (and I am not allowed to in all options).

What happens if you click on + sign from top of your first picture?

Sure, that is how to add items to the list but my point is that they do’t necessarily show up when I go to make a scaled drawing. Looks like I have to choose specific Length and Units. even then, the list does not appear the same, probably because I seem to have duplicates. There isn’t much logic in the way the list is ordered and parsed. Why are there different means of describing different scales (equals and colons)?

I just went in to edit my list. I find that I can add or delete but not edit. So I would like all my scales to use colons as that would hopefully put them in ascending order. But the only input option seems to be an equals sign. I’m not sure how I even got colon ones, unless they were there by default.

This may be a mac based problem. If I were designing this, I would just have the numerical data (1:10, 1:12, 1:50, etc) as in the parentheses. It’s just so visually muddled the way it is.