What is my salary expectation in Germany with Remuneration group 11 TV-H, if I have master degree?
The "stage of remuneration" (Stufe, table column) increases after having worked N years in your current Stufe, i.e., you go to Stufe 2 after working 1 year in Stufe 1, then you go to Stufe 3 after two additional years in Stufe 2, and so on.

This only counts paid work done in public service (öffentlicher Dienst). It is not there to reward "having experience in the field" but to reward "staying for a long time in the job". Unless you had a full-time TV-H11 job for more than a year during your Master studies (which is not allowed), experience as a student will not count towards starting at a higher Stufe.