Transcription:

The player begins with a single unit-if that hand is won,
the player has turned a one-unit profit, and the series
ends.

If the player loses a hand, the wager remains the same
until another hand is won, at which point it's increased
by one unit. This continues until the player winds enough
hands to recoup all previous losses, and come out one unit
ahead, at which point the next hand is considered the
beginning of a new series.

Here is an example of a series that persists for a dozen hands


# BET RESULT BALANCE
1  1   LOSS   -1
2  1   LOSS   -2
3  1   LOSS   -3
4  1   WIN    -2
5  2   WIN     0
6  3   LOSS   -3
7  3   LOSS   -6
8  3   WIN    -3
9  4   LOSS   -4
10 4   LOSS   -8
11 4   WIN    -4
12 5   WIN    +1


In this sequence, the player wins 5 out of 12 hands - slightly
less than the expected average - but concludes the sequence
with a one-unit gain. The consistent-wager player would have
emerged at a net loss of two units, and the Martingale player
would have emerged with a net gain of five, but would have been
required to bet as many as eight units on a single hand.

you should play for break even or +1, cuts the risk of the progression going crazy

I agree betting 1 unit on a win is less risky of blowing a bankroll out - but for that to effectively work you'd need to hit a massive win streak to recoup a bad session.

I was merely pointing out that the example didn't match the explanation.
8  3   WIN    -3
9  4   LOSS   -4    <-- here on step 9 it states the bet was 4units and it was a LOSS therefore the -3 would decrease to -7 not the -4 stated... that's all

That is correct. Spin 6 should have only 1 unit bet since the goal - like a Pluscoup - is to be 1 unit ahead after a betting sequence.

This method of money management is actually very sound, assuming that you have a good stop-loss strategy. Typically, I would lose up to 10 units and revert back to 1 unit bet.