You are right, He misunderstood about the concept of kelly criterion
the %K is amount of % of loss, your understanding were right.

the reason he got 100% from the formular because his calculation base on asset price not his portfolio and that not correct.

The right way to use kelly criterion is use the %K as percent of actual loss

In his calculation the %K = 20 mean he have to take risk 20% a time

but he thought %K is the % of allocation which mean
20% of allocation * 20% of asset risk = 4% loss in portfolio

According to his result 100% from second formular
=100% of allocation * 20% of asset risk = 20% loss in portfolio
which is correct according to the Kelly criterion

the second fomular

Kelly % = W/A – (1 – W)/B

also right but actually is a rearrange of kelly which is

(%W-%L/R)/%of asset risk

= normal %Kelly/%asset risk

which is ratio of require risk to asset risk

Example:

%K = 20% as above example
%asset risk = 20%

from formular %allocation = %K/%asset risk
=20%/20% = 100% allocation