Ahh, I've got it. The bump is in February, right? Leases are monthly price, paid each day.
If lease is 868k/month, that's 196k/week in Jan & March, 217k/week in Feb. That's a ~10.7% increase.
If airline's been roughly same size for a couple of years, bet you see a bump every Feb on the monthly view for however long it shows.
you can see a slightly smaller bump in Nov 94 on the graph you posted, too. 30 day months are 3.33% more expensive to lease per week than 31 day months.