Bowler limit "auto" is one fifth of the innings, rounded up (8 in a 40-over match, 10 in 50 overs, 4 in a T20). It follows the overs if rain shortens an innings.
G50 is only used when the side batting second gets more resources than the side batting first. "Auto" minimum is 20 overs in a 40 or 50-over match, half the overs in shorter matches and 5 in a T20. Follow your league's rules if they differ.
4 and 6 are boundaries (no change of strike). Use 5 for overthrows; for 4 all run, tap 4 then ⇄ Strike if the batters ended at the other ends.
New to the rules? Read the scoring guide. Your finished matches are listed under My results.