pension for study years

Hi, The DRV wrote me that I can pay until I am 45 years of age retroactively for my study years to have them as assurance years. However, they took only the study years in Germany (Hochschulsemester) and not those abroad (Fachsemester). I am going next week to visit them. Does anyone have experience with this? I might ask also find your pension since I go to Karlsruhe. thank you and kind regards Maria