What is the approximate batch size/OG limit for US-05 11g packet? Have I used enough?

I've started a brew with an OG of 1.065 in a 23L batch. I pitched a rehydrated 11g pack of US-05 and after 5 days I took a FG reading when I observed no bubbles after some time; it came out at 1.028 - quite a bit higher than expected (target FG is 1.012).

So, I upped the temperature of my fermenter having realised I only set it at 17degC (oops, I meant to do 19degC but I'm hoping it won't be too much of a problem - it's a versatile yeast I hear!) as well as doing a pretty vigorous swirl of the fermenter to kick up some of the yeast cake. Came back a few hours later, hoorah, bubbles! I'm aware that bubble rate is a terrible way of judging fermentation stage (atmospheric temperature and pressure being factors but both have been consistent over the past week) but going from no bubbles to bubbles after doing this can only be a good thing!

I was/am a bit worried that I didn't pitch enough yeast for this OG since the Brewers' Friend yeast pitch calculator said I was short by about half the cells required - maybe I'm just being paranoid?!

Question(s) - Will I be okay in getting nearer to my FG? In general, from experience or otherwise, what are the upper limits on OG and batch size for an 11g packet of US-05 before I need to think about adding a 2nd packet?

Thanks!