Here are my analysis [Producing results which DO NOT match the values given in the table ]
Lets assume the loss from port 1 to port 2 is 1.72db . Since its a loss , I take it as -1.72db .
Using (db)=20 log V2/V1 we get V2/V1 =0.82 or V2=0.82V1
Now , this implies for a 2 way unequal power divider , V3= (1-0.82) V1 i.e. V3= 0.18V1
Converting this 0.18 into db gives -14db
Thus for a 2 port unequal resistive power divider , if S21= -1.72 db , then S31 = -14db
***The paper says S31=-20db
and also the table values do not match