1500 oil level, dipstick

Hi guys, I have what may be a silly question here. The dipstick for my 79 midget, stock 1500, has a cut out on the bottom below the two level indicator lines. To completely insert the dipstick, I push it down until the coutout stops it from going any further, then rotate it about 90 degrees and insert it the last inch or so. My questions are 1) is this a standard dipstick? 2)Should I read the oil level with the dipstick completely inserted or at the first stop? I have always read the dipstick when completely inserted.

Any insight is appreciated.

Cheers,
Todd