I think the issue here is that you are not specifying from which scope the timestampeee variable must be pulled from when logging it out.
If you’re writing it like this it implies that it is declared in the same Scripts sandbox (like moment for example) whereas you’ve assigned it to the global scope.
To print it out use pm.globals.get("timestampeeee") instead.
More information about variables and scopes can be found here:
https://learning.getpostman.com/docs/postman/environments-and-globals/variables/#variable-scopes