Ive been going to the gym since last year but not really on a focused routine

So i started the stronglifts 5x5 today as recommended

When i got into the gym the squat rack was taken so i figured rather than hanging around i would use the smith machine

I know the smith machine usually makes the exercises easier than the free barbell so i wasnt really sure how much weight i should put on to replicate the recommended starting point of 20kg

So i just put 5kg on each and started from there

My question is does anyone else use the smith machine for there workouts and could shed some light on this please?

Thanks in advance