interpreting rental property calculator graph

[Doug Davis]

I have been trying to use the BiggerPockets rental  property calculator and interpret the graph.  This doesn't look like the best home to buy, but where I'm having a problem is interpretation of the graph.  Green is income, orange is expenses.  The two meet a little after the start of year 10.   The black line appears to be cash flow.  Why doesn't the black line cross zero at the same time the green and orange lines cross each other (expenses=income)?  Thanks.