Two phase flow engine

Hi every body

I have to get the SWRC curve base on the experimental test (Pressure Plate ). It is vital to define surface tension which is physically
equal to 0.0728 (N/m) for water, however I have seen in one of the examples (drainage-2PFV-Yuan_and_Chareyre_2017) that surface
tension is equal to 10 (line 127). I've changed the number of surface tension, for example it was multiplied to 4 (0.0728*4) and then result became better since, the type of soil is fine-grained.Therefore I came up with these questions :

1) Why in above-mentioned example surface tension is equal to 10? Is it unit-less?

2) why when surface tension increased (0.0728*4 )sample drained slower? It means water content decreased slowly while, when surface tension is equal to 0.0728 water content drop sharply!