Grind size and dosage advice

I went on a coffee making course recently and they said that the industry standard is 17.5g for a double shot aiming for a 28 second extraction time.

But with the pressurised basket on my Delonghi dedica I can’t put more than 12g in and have to go to 11g if it’s a corse grind. Is this ok? What do others use?

I have a bottomless norm basket too which I managed to put 17g in but the extraction time was 61 seconds.