Welcome to planDisney, Jesus! Mickey Mouse says that "Arithmetic is being able to count up to twenty without taking off your shoes." I think it's safe to say that your math skills are a little more advanced than his (and mine, too)!
I'm sad to hear you won't be able to use all days on your multi-day
theme park tickets. As you noted,
wholly unused Disneyland Resort Theme Park tickets may be applied towards purchasing a new Theme Park admission ticket. Unfortunately, the rule applies to the whole ticket and not individual park entries. Disneyland does not issue credit or refunds for partially used tickets, which yours would be considered since three of the days were already redeemed. Also, with the multi-day tickets, once you enter the parks, you have 13 days to use the remaining days.
I realize that this is not the answer you were hoping to hear, Jesus. However, when you are ready to travel to the Happiest Place on Earth again, check the
Special Offers page on the Disneyland website. Sometimes you'll find discounted multi-day tickets for Southern California Residents (zip codes 90000-93599) or Golden State Residents (all California residents).
If you have any other questions, Jesus, please feel free to ask anytime! We hope to see ya real soon!
Eean