Pair Analysis in PSI

Hello Dear Friends,
I am using Sarproz ans using PSI now. But I have 2 critical questions and if you answer , I really be happy.
1- There are pairs calculation “Time series CVS” created by Software . Is this results with respect to master or with respect to former image ?
For instance , I have 3 images and have these deformation values
2017/02/01(Master) 2017/02/25(Slave) 2017/04/26 (Slave) 2017/05/08 (Slave)
0 -0.5 2.1 - 0.76
For 2017/02/01 : It is the difference between 2017/02/01 and 2017/02/25 ?
For 2017/04/26 : It is the difference between 2017/04/26 and 2017/02/01 OR It is the difference between 2017/04/26 and 2017/02/25.
2- For each pair difference calculation, PSI is using one linear function or for each pair it creates different linear function?
Thank you vary much

Maybe you should ask this in the sarproz forum:

Thank you @ABraun, I asked to the Saproz Forum and they responded like that:
1- Time series each pairs is wrt to master
2- Software creates only one linear function and estimate the pairs wrt that linear function.