Lyft DOES NOT! report to Skeddy the actions you're doing in the Lyft Driver app, so the ride you're canceling in the Lyft Driver app is going back to the market, and there is a good probability for the Skeddy to find it and assign it back to you.
Then, if you don't SKIP the returned ride again in the Skeddy app while not actually making this ride, the credits will be deducted for that not skipped ride.
To avoid this happening, please always SKIP! the unwanted ride in the Skeddy app, instead of canceling it in the Lyft Driver app. This way, the Skeddy will know that you don't really want to make this ride, so it will never be returned back to you.