Think about it. How many people add a quart of oil (or more) to their crankcase having no idea of what oil (brand, age, mileage, type, viscosity, etc.) is already in there? Just be close. It happens all the time. Where are the broken engines? They don't exist.
Mix the oils and be done with it. Next time, buy the correct oil and change it per the schedule. Spend your time/worries on more important things. Google "BITOG" if you insist on obsessing about it. IMO, you can spend 1,000 hours at BITOG and know less about oil than you do now!
Chum lee