I've noticed that the income v. expense report shows the income under the month it was actually earned rather than the following month which it is budgeted for. this completely throws off the income v. expense concept to determine if you spent more than you earned in that month. I would think that since the YNAB method is so heavily encouraging using last month's income, that this report would reflect your selection of income for this month vs. next month correctly.
example. I got a check for 1000 in january, it's set up as "income for February". During february I spent 900. In February I only earned 800 and set it for "income for March". On the income v. expense report it shows that January income was 1000, February income was 800 and expense was 900, equaling an overspending of 100. This is not correct because during february I was using the 1000 income from january's check. so it should show february as 1000 - 900 = 100 savings.
If this isn't a bug then i'm pretty confused as to why it would be set up that way