Refund value estimation for one leg of the return journey
Upvote:2
Not much you can do besides:
Asking for evidence from MakeMyTrip on how they calculate the refund, and their logic and reasoning for it.
Ask SpiceJet for a letter stating what the refund should be, if they have a policy on this and are willing to do it.
If you can prove they're skimming off the top, you can then take them to a disputes tribunal / court, given the original letter, and they'll likely have to justify the change.
Consider tweeting them about it. Often the public attention gets you more help.