Use Undersize Bearing Usage Guide: Notes

WARNING: This page is about a different car, the 2002 Nissan Altima. However, it is still accessible from the selected car via links, so may be relevant.

Use undersize (U.S.) bearing when oil clearance with standard size main bearing is not within specification.
When using undersize (U.S.) bearing, measure the bearing inner diameter with the bearing installed and grind journal until oil clearance falls within specification.