No problem - always happy to help. As a general rule, dose of coffee grounds in and dose of espresso out are certainly not set in stone. Different baristas will use different ratios of coffee grounds to espresso depending on both the drink they are making and the individual beans.
A common starting point is 18-20g of coffee grounds in, to get 36-40g of espresso out the other end in around 30 seconds. It varies, but I believe most would recommend that 30 seconds should start when the first drop of espresso hits the cup. For us using a BDB, that means taking note of how many seconds are on the shot timer when that first drop hits - and for me that's typically around 7-8 seconds - and adding that on to the shot time.
Hence I usually end up, when pouring a normale espresso (one with a 1:2 ratio as above), getting 36g of espresso from 18g coffee in around 38 seconds.
An excellent reference can be found below, which I found really useful.Espresso 101: How to Adjust Dose and Grind Setting by Taste
Let me know how the shots turn out with 18-20g in the basket. If you get stuck, post a couple of pictures or better yet a video and I'm sure we can give you some pointers.