Likelihood Rating Scale- Calculation of Probability

[Andre833]

I came across the following table on page 6 from publication at : https://www.researchgate.net/publication/320008411

Ranking__Probability_____Description
1________0.00001_______Improbable unlikely to occur at all
2________0.0001________Remote - once in 100 to 1000 years on one ship
3________0.001_________Rare once in 10 to 100 years on one ship
4________0.01__________Occasional - once in 1 to 10 years on one ship
5________0.1___________Frequent once in one year on one ship

I am confused at how the column on probability is calculated in the table.

Example, if definition of rank 4 is it happens once in 10 years, the probability is 1/10 = 0.1. How did the table state 0.01?
Is my interpretation of once in 10 years = 1/10 is the calculation of frequency?
So how is the table column probability number being calculated.