Hi, the natural sign at the end of the eleventh bar (first bar in line four) is not existing in the original text (and doesn't natural f sound wrong to your ears?). Also the bar is noted to be 10th at the start of the line, but with three bars in the third line (which correctly starts with bar 8) we come out at 11 in the fourth.
here's a copy of the page from the first print in 1741 https://upload.wikimedia.org/wikipedia/commons/2/27/Quodlibet.jpg
