Units are a measurement of the recommended stake without mentioning the real sum of money because stake differs a lot between different players and what someone stake in real is maybe 0,1% for the other one. So units are the best option for a recommendation as everyone has different bankroll and money available to invest.
Every single unit is a different percentage of your bankroll, where 1u is 0,5% and max 10u is 5% of your bankroll. This is the safest and most successful method of raising your bankroll in the longterm period.
Example #1
If you have a bankroll of 1000 EUR, then the scale of the unit will be as follows:
1u = 0.5% (5 EUR)
2u = 1% (10 EUR)
...
9u = 4.5% (45 EUR)
10u = 5% (50 EUR)
Note:
As time goes your bankroll would be different so you need to recalculate your stake per unit for newly updated bankroll. This kind of strategy & money management prove to be the best option in longterm profit run, we just need strong patience to manage it.
Example #2
Let's say you raise your bankroll for 200EUR using this strategy and you decide to update your staking plan. This means with 1200EUR totally in your bankroll you would have this:
1u = 0.5% (6 EUR)
2u = 1% (12 EUR)
...
9u = 4.5% (54 EUR)
10u = 5% (60 EUR)
Note:
You can see and understand that your profit would grow slowly but progressively as your stake size is bigger which gives you more profit than it was before what is a big benefit from this strategy.