When using your discount card effect in Kumos shops, your lifetime savings are now tracked in both the new Effects system AND the legacy counter (shown in your Discount Card stats). This ensures the "Total sP Saved" stat stays accurate no matter which shop system you use.
If I "migrate" the twenty percent discount card I have had locked in my inventory for many years, will it give my discount both on the legacy site and kumos, though? It's prompting me to use it as an effect, but I'm not sure I want to do that if I'm going to lose my discount on legacy Subeta.