First, you can put any whole number (no decimal) in the quanity, e.g. 17, 45, 90. In fact, you wrote above that you can write for 90, but you can't write for 90.
In 5.0.28 and 5.0.29 you can not add the units such as grams, tablets, cc, mLs, etc. As far as whether you have to write grams or cc in the comments section, you do not in order to make the script valid. Whether you do depends on your pharmacy. Most pharmacies (especially when they get used to scripts coming from you) will understand that 150 = 150mL if you write for Cefzil suspension and that 6 = 6 tablets if you write for Z-pack.
There is no reason it should not take 100, 45 or 90. Make sure you do not have a space after it. For instance, if you type 90 grams, but then realize you can't write grams and then back space over grams but leave 90_ where underscore = a blank space, then it won't work.
If you read this site:
http://amazingcharts.com/support/i-want-to-help-myself/current-beta-version/it will tell you what to expect it 5.1.6, which will allow you to use units.
Please tell us more about your issues with 30 working where 45 won't. I write for that all the time.
