[NEWBIE] What is a daily timeframe I should be shooting for, for practice?

I’m on day 4 of this journey of learning guitar and my fingers expect brutality, but it seems I’m good for about 15 minutes then I have to stop for a bit, then I’ll hit the next 15 minute session. Nothing can be done now (as I just started) but I assume after a couple weeks I’ll be able to feel my fingertips again and be able to play for longer durations?

I also discovered I absolutely hate the casual posture. I was really struggling to get my wrist around the neck, then thru research (I’m teaching myself for now) discovered the classical posture. Ooooh boy, game changer.

Any tips for increasing practice time and markers for goals & progress? Thanks! https://imgur.com/a/EsmaYyQ