In the Bachelor's programme with two subjects, students combine two equal subjects of their choice. The programme conveys solid basic knowledge, e. g. to continue with a Master's programme in one of the chosen subjects to expand their knowledge. The Bachelor's programme with two subjects and the "studium generale" track has more freedom of choice than with the "teaching profession" track, however it naturally does not reach the breadth of expertise as the Bachelor's programme in mathematics (B.Sc.).
Attention! In some subjects, the completion of the Bachelor's programme with two subjects automatically allows the transition to the corresponding Master's programme. This is not the case in mathematics: The studies can be structured such that the transition to the Master's programme in mathematics (M.Sc.) is possible, but not every individual arrangement of the Bachelor's programme with two subjects allows you to do so. Therefore, you should plan the courses to take at an early stage together with the study advisor.
You can find a lead on how such an arrangement can look like here: Entrance requirements for the Master (M.Sc.) in mathematics, if you completed a Bachelor (two subjects) with mathematics.