Hey WPREadmin
The prefix and suffix are used when you present points on your site and is purely optional.
Example 1: Using prefix / suffix:
You have 10 pt. (pt. being a suffix here)
You have $ 10. ($ being the prefix here)
Example 2: Not using prefix or suffix:
Your current points balance: 10
It all comes down to how you want to present your points. The prefix and suffix are added to the numeric value just for presentation and has no effect on how points are gained or used.
Some users use myCRED points as a form of currency so in these cases adding a symbol or words help to format their points accordingly.