units and definition of AWATER in counties function?

[CCheCastaldo]

How do determine the units for the AWATER variable in:
boundaries <- tigris::counties(cb = FALSE)
head(boundaries)
Simple feature collection with 6 features and 17 fields
Geometry type: MULTIPOLYGON
Dimension: XY
Bounding box: xmin: -123.7283 ymin: 18.11774 xmax: -65.81565 ymax: 46.38562
Geodetic CRS: NAD83
STATEFP COUNTYFP COUNTYNS GEOID NAME NAMELSAD LSAD CLASSFP MTFCC CSAFP CBSAFP
1 31 039 00835841 31039 Cuming Cuming County 06 H1 G4020
2 53 069 01513275 53069 Wahkiakum Wahkiakum County 06 H1 G4020
3 35 011 00933054 35011 De Baca De Baca County 06 H1 G4020
4 31 109 00835876 31109 Lancaster Lancaster County 06 H1 G4020
5 31 129 00835886 31129 Nuckolls Nuckolls County 06 H1 G4020
6 72 085 01804523 72085 Las Piedras Las Piedras Municipio 13 H1 G4020
METDIVFP FUNCSTAT ALAND AWATER INTPTLAT INTPTLON geometry
1 A 1477644346 10691216 +41.9158651 -096.7885168 MULTIPOLYGON (((-96.55515 4...
2 A 680980770 61564427 +46.2946377 -123.4244583 MULTIPOLYGON (((-123.7276 4...
3 A 6016818946 29090018 +34.3592729 -104.3686961 MULTIPOLYGON (((-104.8934 3...
4 A 2169272978 22847034 +40.7835474 -096.6886584 MULTIPOLYGON (((-96.68493 4...
5 A 1489645185 1718484 +40.1764918 -098.0468422 MULTIPOLYGON (((-98.2737 40...
6 A 87748418 32509 +18.1871483 -065.8711890 MULTIPOLYGON (((-65.85703 1...

I couldn't find any mention of this in the documentation. I assume this is the area of water in each county? Thanks, I appreciate it.