原來係咁....

You may say:
1. Oh, I see. You had studied in an/the university before.
2. Oh, really! You did study in an/the university before.
(use " the " for the particular university you talk about)

Use no. 1. for a general tone; and no. 2 for emphasizing your surprise. The word " did " is to emphasize " 原來 "

Oh, originally you have read the university

哦,,原來你讀過大學-
ooh...you have been in college....