California title underwriters have relied upon the following principles:

1.  The date and time stamp show priority.

2.  When the date and time stamp are the same, then the county assigned series number is the second default.

 In most CA counties, multiple title companies record documents at 8am every day, as the county provides a set-back time to 8:00 a.m.  While all the papers are handed to the county staff by 7:50 a.m., the actual processing time is around 11:00 a.m. because of the time needed to rectify minor document errors (pages out of order or misoriented, illegible notary seals, need for cover pages, etc...,) and the time to clear the index of last-minute lien matters recorded on the prior day ("name runs"). 

This means that, without the set-back time to 8am, such papers would record after many mailed liens are processed and many public-persons' papers are walked in.  Thus the time established priority, despite the numbering appearing serially AFTER those other mentioned papers.

But, since all the title companies effectively record concurrently at 8am, the priority then goes to the serial number.

 Some states are not "first to the counter" states, so this will vary.  What did Ohio say in the ruling?