Hello and hope you are doing well.
The concern for the size of polyps is to see if they are cancerous or not. Polyps greater than 10 mm are considered to be at risk for cancer, though this is rare. Hence surgical removal is advised for polyps greater than 10mm. But for smaller sized polyps if they are accompanied by gallstones, then cholecystectomy is advised. So, don't worry and follow up to see for changes.
Hope this helped and do keep us posted.