I suspect that what's happening is you've placed e.g. the string "50,20" into a cell rather than a pair of numbers.
There are several ways of converting a string of comma-separated numbers into a proper list. For example,
"%i,%i" parse "50,20" 0 + "," split "50,20" eval["50,20"].value # (this is opening a walnut with a sledgehammer)
Alternatively, if you want to store structured data within a grid cell, you can specify a column's format as "j" (JSON data) or "J" (LOVE data, a superset of JSON) and then enter your pairs like so in CSV mode:
or like so in JSON mode:
