There's a custom field (selection type) with 4 values in the selection.

Red

Yellow

Green

White

If you select multiple, the data displays as:

Red, Yellow

If you copy and paste that data to another action card it shows up as:

Red,Yellow (without a space)

This adds a new value (Red,Yellow) to the list of selections in the settings for the custom field instead of selecting both values Red and Yellow.