BBCode size tag problems

I noticed that the BBCode size tags were not working on my site when used as illustrated in the help text:

You said: [size=20]HEY![/size]

When I looked at the bbcode-filter.inc file, I noticed that the filter for the size tag did not include the "px" unit in the final code ... in other words:

"font-size:20"

appears in the source code instead of

"font-size:20px"

Rather than edit the filter, I tried entering the unit within the BBCode size tag, as follows:

You said: [size=20px]HEY![/size]

This worked great. So I tried it with ems, and it also worked. (Not a bug, but a feature, apparently.)

Problems:

1. The help text needs to be updated to explain the need for including font size units.
2. There doesn't seem to be a check on how large the font can be, even though the help text says to enter a number between 10 (the smallest) and 30 (the largest). If a user enters 20px, that's no big deal. But if an inexperienced user enters 20em, that can be a BIG problem.

For my site, I'll probably just restrict it to pixels and add the "px" unit to the bbcode-filter.inc file. But I wanted to open an issue in case anyone else runs into this problem.