For instance if you want 20% that could also be expressed as a fraction such as 20/100, which turns out is the same as 2/10 or 0.2.
I do think they should remove the redundant statements in the conditions and also have an assertion that guarantees percentage to be [0, 1].
> The term "percent" is derived from the Latin per centum, meaning "hundred" or "by the hundred". The sign for "percent" evolved by gradual contraction of the Italian term per cento, meaning "for a hundred". The "per" was often abbreviated as "p."—eventually disappeared entirely. The "cento" was contracted to two circles separated by a horizontal line, from which the modern "%" symbol is derived.
This might be a little more obvious for me since my first language is derived from Latin, but anyhow it still keeps the meaning in english.