What is bankroll management
How do you size bets so a bad run doesn't end you?
Sizing is not a smaller version of picking. It is the thing that decides whether a real edge survives a bad run.
Fractional, always
Kelly gives the growth-maximising stake given the true probability. You have an estimate with an error bar, and the penalty is asymmetric: betting twice the correct fraction has negative growth, betting half has about three-quarters of the growth at a quarter of the variance. Overestimating costs far more than underestimating, and devigged estimates are exactly the kind that get overestimated.
Cap every bet regardless
Kelly on a genuine 30% edge and on a stale line ask for the same stake. The cap is what makes the difference between them survivable.
Count correlated bets once
Kelly assumes bets resolve one at a time. Twelve overs riding one game script is one undiversified position wearing twelve hats, and sizing each at its individual optimum is a far larger bet than it looks.
Judge the sizing separately from the picking
Money return and flat-bet return answer different questions: what happened, and what would have happened staking level. The gap between them is the only direct read on whether your sizing earned anything, and almost no tracker separates them.