PROBLEM OF SINGLE AND DOUBLE COFFEE MACINATURE

Good evening everyone
, I am new to the Forum and new to the world of coffee.
Since a few days at home I have a Lelit Grace and a Lelit PL043 coffee grinder.

I bought 4 types of coffee to try my hand at various tests and find a pleasant aroma to my palate.

After several grindings I thought I had found the right one using the single coffee filter: about 7Gr and grinding at 2.1...25ml in 25 sec. a good color, a nice cream...in short a good start.
Then this morning I started to make two coffees so I kept the same parameters changing only the amount of ground (14gr) and obviously the filter for two cups.
The result was disastrous!!!! not even a drop of coffee came out. is it possible that

for the single there is a grind and for the double another? it seems strange to me.... for the double I have to
grind almost to 3! Can someone

help




me?






Thank you all very much.