It is a phrase used to express acceptance or agreement, often with a hint of skepticism or sarcasm.
Here are some examples of how it can be used:
* "Si lo dices, pero no me parece." (If you say so, but I don't think so.)
* "Si lo dices, entonces no voy a discutir contigo." (If you say so, then I won't argue with you.)
* "Si lo dices, pero yo lo he visto con mis propios ojos." (If you say so, but I saw it with my own eyes.)