Pre seed - how much to use

[JS5]

This might be a stupid question but here it goes. The instructions say insert 15mins before and the size of a quarter, what does that mean, how could you tell its size of a quarter when the tube is long and not shape of a quarter ?

Also those that used preseed and got bfp, how much did you use?

I'm ttc #2 at the moment but I used it for my first baby. I did 2 months without preseed and then on the third month I used it and fell pregnant. I used between 2-3 on the applicator and this seemed about right.

I used it last cycle this time around and it didn't work but I wasn't tracking and just going off my app so I could have got my ovulation dates wrongs. I've used it again this cycle as it helps when dtd alot in a short period of time!

Is it American? Are they describing a 'quarter' as in a coin?