As others have said, just be consistent.
In my health articles (which provide a lot of data, but are not exactly "technical" writing), I often use amounts with units; I also often use from...to, like:
5-15 liters or
from 5 to 15 liters. This is the way I'd like to write, and not
five to 15 liters. I tend to avoid 5-15 L, since many readers could ask what's "L."
Below are not my claims, they are quotes of rules from
grammarbook.com, just to add to the confusion:
1. Spell out single-digit whole numbers. Use numerals for numbers greater than nine [so, not ten?].
2. Be consistent within a category. For example, if you choose numerals because one of the numbers is greater than nine, use numerals for all numbers in that category. If you choose to spell out numbers because one of the numbers is a single digit, spell out all numbers in that category.
Correct example:
Given the budget constraints, if all 30 history students attend the four plays, then the 7 math students...
Incorrect example:
I asked for five pencils, not 50.