County to County Mobility Data

Hello! I am currently researching COVID infection rates and how they are effected by mobility, on the county level. I am digging into the sample data for the Neighborhood Patterns - US from Advan. From my understanding, the first 5 digits in the first column, labeled Area, are the FIPS code for the county. Similar numbers/digits can be found in a series in columns K through T (DEVICE_HOME_AREAS to DEVICE_DAYTIME_AREAS). I am hoping to get some clarification on why these values are listed this way. Is it the area code (CBG) followed by the number of devices? What is significant about all of the CBGs listed in the same series and under the same original CBG, seen in the first column? Does this series mean that a certain amount of devices are travelling to a different CBG? How could I figure out what the mobility is on a county-level?

I would appreciate any insight and breakdown of this particular data set. Thank you!

Their Neighborhood Patterns Documentation may help clarify how some of the column attributes work.

The first column is the CBG of interest. The other attributes list the number visitors/devices that come from that or other CBGs in the given time period (month).