Calculate how much current is a microcontroller's pin drawing
You calculation is based on the assumption, that the RA0 pin will sink the current. But this is only true, when the pin is configured as an output and driven low.

Since pin RA0 apparently is sensing, whether the button is pushed, the pin is likely to be configured as an input. In this case almost no current (only some leakage current) will flow when the button is open.

The table you are reffering to shows the absolute maximum ratings. Your pins should never sink/source more than the current given there.