If bets were placed on the toss of a coin, the probability of heads is 50 %, the probability of tails is 50%. In terms of bookmaker decimal odds, 50% probability is expressed as odds of 2.0. Which means that if bets were continuously placed on either heads or tails at odds of 2.0, over the long term the bankroll would break even

However, if odds of 2.1 were available from the market, the odds of 2.1 are miss priced as they are greater than 2, which means a positive odds edge is available. The correctly priced odds are 2 which is a probability of 50%, odds of 2.1 is a probability of 47.6%, which means a positive odds edge of +2.4% (50% - 47.6%) exists

Heads and Tails

Fair value & positive odds edge

Fair Odds

Heads
Probability 50%
Odds 2
Heads
Bet Result P&L
Spin 1 £1,000 Win £1,000
Spin 2 £1,000 Loose -£1,000
Spin 3 £1,000 Win £1,000
Spin 4 £1,000 Loose -£1,000
Spin 5 £1,000 Win £1,000
Spin 6 £1,000 Loose -£1,000
Spin 7 £1,000 Win £1,000
Spin 8 £1,000 Loose -£1,000
Spin 9 £1,000 Win £1,000
Spin 10 £1,000 Loose -£1,000
Return £0
Tails
Probability 50%
Odds 2
Tails
Bet Result P&L
Spin 1 £1,000 Loose -£1,000
Spin 2 £1,000 Win £1,000
Spin 3 £1,000 Loose -£1,000
Spin 4 £1,000 Win £1,000
Spin 5 £1,000 Loose -£1,000
Spin 6 £1,000 Win £1,000
Spin 7 £1,000 Loose -£1,000
Spin 8 £1,000 Win £1,000
Spin 9 £1,000 Loose -£1,000
Spin 10 £1,000 Win £1,000
Return £0

Positive odds Edge Heads

Heads
Probability 47.6%
Odds 2.1
Heads
Bet Result P&L
Spin 1 £1,000 Win £1,100
Spin 2 £1,000 Loose -£1,000
Spin 3 £1,000 Win £1,100
Spin 4 £1,000 Loose -£1,000
Spin 5 £1,000 Win £1,100
Spin 6 £1,000 Loose -£1,000
Spin 7 £1,000 Win £1,100
Spin 8 £1,000 Loose -£1,000
Spin 9 £1,000 Win £1,100
Spin 10 £1,000 Loose -£1,000
Return £500.00
Tails
Probability 52.6%
Odds 1.9
Tails
Bet Result P&L
Spin 1 £1,000 Lose -£1,000
Spin 2 £1,000 Win £900
Spin 3 £1,000 Lose -£1,000
Spin 4 £1,000 Win £900
Spin 5 £1,000 Lose -£1,000
Spin 6 £1,000 Win £900
Spin 7 £1,000 Lose -£1,000
Spin 8 £1,000 Win £900
Spin 9 £1,000 Lose -£1,000
Spin 10 £1,000 Win £900
Return -£500

The example does not include variance in the results