What the Kelly criterion does
Kelly sizes a stake by how big your edge is relative to the odds. With decimal odds o and win probability p, the full Kelly share of your bankroll is (b·p − q) / b, where b = o − 1 and q = 1 − p. No edge means no stake.
Example: odds of 2.30 with a 50% chance is an edge of +15%. Full Kelly says 11.5% of the bankroll, half Kelly 5.8% and quarter Kelly 2.9%.
It's only as good as your probability
Kelly takes the probability you enter at face value. If you overestimate it, Kelly overbets, and an overestimate of a few percentage points can turn a sensible stake into a reckless one. That's why a fraction of Kelly is the sensible default.
Full Kelly also has large swings: losing runs that cut the bankroll by a third or more are normal along the way, even with a real edge. Most bettors use a fraction. Sharp Bets uses half Kelly and shows stakes in units of 1% of the bankroll.
Where the probability comes from
A price only has an edge if your probability is better than the bookmaker's. The most reliable estimate available is Pinnacle's line with its margin removed. The EV calculator does that step and then sizes the stake the same way.