The use of "that of" with a percentage

Question

DHT concentration with the Low Carb diet was 58% that of the CRPC-bearing mice on the Western diet.

I know a comparison is made, but I don't know if it is saying that the low carb diet was 58% more, or less, than the western diet.

Answer 1

If A is 58% of B, that means that A = 58/100 * B. "That of" is used to refer to an aspect of something. In this case, it refers to DHT concentration, so the whole thing means "DHT concentration with the Low Carb diet was 58% of the DHT concentration with the CRPC-bearing mice on the Western diet." So a little more than half.

"A is 58% less than B" and "A is 58% more than B" are used to refer to percentages greater or less than 100% of B — 42% of B (so less than half) and 158% of B (so more than one and a half times) respectively.

This also applies to other fractions. "A is a third more than B" means A is one and one third times as much as B, but "A is a third of B" means A is just one third times as much.