The english description says the same thing but if you read, its lowest hp % not lowest HP

It means the lowest % of HP remaining.

I have one hero with 100k HP and one hero with 80K HP, they go into battle and both drop to 60k HP, then the hero with 100k HP has the lowest HP %

100k - 40k HP = loss of 40% HP equals 60% remaining

80K - 20K HP = loss of 25% hP equals 75% remaining