Stacked bar chart y-axis total shows incorrect value for same data set as a table?

I am computing running totals by month and want to display the data in a stacked bar chart. I noticed this issue when looking at the total for 06/30 (which i know to be just over 7 billion), but in the chart the total in the y-axis is shooting up over 8 billion. When I put the data in a table just to see what values are being added up to get this incorrect number, to my surprise the calculation is correct at just over 7 billion. Why would this suddenly be different in a visual? Proof is below