Hi John,
Both format and replace are standard python string functions
I used the string number formatter to format the number with commas( , ) and then used replace to replace the commas with spaces.
Learning python is not required for using robot framework, but learning some of the basics is pretty useful, I linked to the W3Schools site rather than the python documentation as I feel that W3Schools explains things better for non programmers, they also have a good python tutorial
Good luck with the learning,
Dave.