During export the Story points assigned to Codebeamer work items can be converted to the "Duration" hours in MS Project. This conversion is only happening if you enter a ratio of how many hours does a Story point worth. That is appearing on the export page:

For example if you enter the number 4 there that means that every Story Point worths 4 hours. So a 2 Story Point value will become 8 hours in the Duration of the appropriate MS Project task.

Note however that Story Points are only converted if the exported work item's Estimage Hours field is empty. This won't overwrite the value there!