Dipstick length ????

[USA69Z]

i been workin on my 70 steppa now for 3 weeks and today i discovered it has a dipstick on both sides for engine oil levels.. ive had a few sbc and never seen this before.. The funny thing is they are different lengths? and im not sure if they are correct..
if any one can tell what length it should be ill plug one up..

mine are - 'tube from top' to where it meets the block is 15'' right side with a dipstick length of 18.5''

tube from top too where it meets block is 14'' on left with a 21'' stick.

hope this makes sense.. im now confused

Gav