according to wiki, the Discretionary data —
may include Pin Verification Key Indicator (PVKI, 1 character), PIN Verification Value (PVV, 4 characters), Card Verification Value or Card Verification Code (CVV or CVC, 3 characters)
This means that it's not guaranteed that I would always be able to get the CVC, which is a problem for me. I was able to use an existing implementation to parse my credit card stripe and got a bunch of numbers for the discrepdata. I'm not sure exactly how to interpret exactly. Since its more than 8 chars and does not match my cvc, or pin number.
It looks like(numbers are random, but the padded 0's are the same): 0000031200100
What does this mean?
You shouldn't use the discretionary data. It is (as it's name implies) entirely optional. Some card schemes simply don't use it at all, and within the schemes that do allow it, most card issuers do not use it. Where it is used you'll find differences in how it is populated, both between card schemes and potentially between card issuers.
Further, the CVC that is on the mag stripe is actually a CVC1 code, which only attempts to verify that the mag stripe details have not been tampered/corrupted. It is not the same as the CVC code printed onto the back of the card.
The CVC that is printed onto the card is (by design) intended to be viewed with eyes only.