Is "less than or equal to" sometimes written with two lines?

Question

I'm reading this research paper and they have the equation like this (0 ≤ λ ≤ 1) however the less than or equal to part has two lines, see screenshot here: http://prntscr.com/s5o0do

I just wanted to ask and confirm that this is just another way of writing "less than or equal to" or if it had a different meaning.

Answer 1

Both signs have the same meaning. $\leq$ is actually the abbreviation of the version with the equality sign $\leqq$. $\leqslant$ is the third variant of it.