Owin object- What is a relative area?

Question

setwd("/shapefiles/uhf")#shapefile obtained from http://sedac.ciesin.columbia.edu/geonetwork/srv/en/cu-gis_metadata.show?id=3569&currTab=advanced#
    `enter code here`map<-readOGR(dsn=".",layer="UHF_42_DOHMH_2009")
    `enter code here`plot(map)

`summary(map)` #shows units are in us-ft#

#convert the coordinate system of shapefile to lat/long#
coordinates(map)
proj4string(map)=CRS("+init=esri:102718")
map=spTransform(map,CRS("+proj=longlat +datum=WGS84"))
summary(map)
. 
> summary(map) #shows units of measurement are in us-ft Below is the output#
Object of class SpatialPolygonsDataFrame
Coordinates:
       min     max
x 913090.8 1067310
y 120053.5  272932
Is projected: TRUE 
proj4string :
[+proj=lcc +lat_1=40.66666666666666 +lat_2=41.03333333333333
+lat_0=40.16666666666666 +lon_0=-74 +x_0=300000 +y_0=0 +datum=NAD83
+units=us-ft +no_defs +ellps=GRS80 +towgs84=0,0,0]
Data attributes:
    OBJECTID       UHFCODE        SHAPE_Leng       SHAPE_Area       
 Min.   : 1.0   Min.   :  0.0   Min.   : 34713   Min.   : 35132269  
 1st Qu.:11.5   1st Qu.:203.5   1st Qu.: 55839   1st Qu.:101843450  
 Median :22.0   Median :303.0   Median : 73089   Median :164519524  
 Mean   :22.0   Mean   :281.7   Mean   : 90960   Mean   :194568186  
 3rd Qu.:32.5   3rd Qu.:403.5   3rd Qu.:113901   3rd Qu.:269127674  
 Max.   :43.0   Max.   :504.0   Max.   :250903   Max.   :731130742  

                              UHF_NEIGH           BOROUGH  
 Bayside - Little Neck             : 1   Bronx        : 7  
 Bedford Stuyvesant - Crown Heights: 1   Brooklyn     :11  
 Bensonhurst - Bay Ridge           : 1   Manhattan    :10  
 Borough Park                      : 1   N/A          : 1  
 Canarsie - Flatlands              : 1   Queens       :10  
 (Other)                           :37   Staten Island: 4  
 NA                              : 1              
#selecting a part of the shapefile#
brooklyn<-subset(map, UHFCODE==205 | UHFCODE==206 | UHFCODE==209,)
str(brooklyn)
summary(brooklyn)

#converting selected shapefile in to owin#
boundary<-as(brooklyn, "owin")
plot(boundary)
summary(boundary) #Below is summary of the output#

Window: polygonal boundary
4 separate polygons (no holes)
           vertices        area relative.area
polygon 1        16 3.35333e-06      0.000764
polygon 2       205 1.10311e-03      0.251000
polygon 3       173 1.69957e-03      0.387000
polygon 4       178 1.58568e-03      0.361000
enclosing rectangle: [-74.04249, -73.9536] x [40.58028, 40.67145] units 
Window area =  0.00439172 square units 

#This codes are run after transferring the TB cases (.csv file) into r #

a<-as(brooklyn_tb, "ppp")
str(a)
summary(a)
a$window=boundary plot(a, pch=16)
summary(a$window)

#compute K and L functions#

BROOKLYN<-Kest(a, correction="trans")
plot(BROOKLYN)

My question is, what is the "relative.area" that appears after converting the shapefile to its own object?
I have to build the latitude and longitude of TB cases in this shapefile and run the Kest () function. I need to know which unit of measure is used to perform Kest () calculations? Is there a way to change units? What is the “r” unit in the Brooklyn section after running the Kest () function? I can’t post images because I don’t have enough “reputation” !!!! But here is a link to a potential K (r) graph: http://rgm3.lab.nig.ac.jp/RGM-files/R_CC/result/spatstat/thomas.estK.Rd_001_large.png