How exact must the info in a warrant be to be valid?

Minor typograhical or informational errors are irrelevant. Only material omissions or discrepancies can invalidate a warrant.

As long as the warrant is signed by the appropriate authority, and as long as it can be reasonably determined that you are the subject of the warrant, and as long as the intent of the warrant can be reasonably understood, and as long as the warrant contains all of the particulars required by law, it is perfectly valid.