Somehow I changed my format to include 4 places past the decimal while using did mm.mmm?

I can only speak to the 66i. The only available format for degrees and decimal minutes IS dd mm.mmmm. 

We’ll I’m guessing I did an update and it changed the setting.  So is there a way to go back to a previous version of the software?  But maybe more importantly, why would they change it to the 4 digit decimal?  I’ve never seen it displayed that way anywhere.  I get that it would be more accurate.   But I’ve never seen anyone list it that way.

It has always been that way on the 66i and on all modern GPSrs. The 4th digit is actually meaningful. At 40 degrees north, .0001 degree of longitude is about 28 feet. .0001 degree of latitude is about 36 feet (uniformly). GPS should be good to 15 feet or so. 

Hmmm... 

How did you get those numbers?

My Geospatial calculator suggest that 00°00.0001' equates to about 0.604629 ft of latitude and 0.608610 ft of longitude at any location along the equator.