I am reading the chapter of Entropy, but the calculation here is killing me.

first of all, i think the calculation on the screenshot above is correct. What confuses me is the two pics below.

The calculation of H(L1) is exactly the same as the picture above, but the result is doubled.

And -1/4 log2 1/4 = 1/2 -3/4 log2 3/4 = 3/2 log2 3
Am I confused? Someone helps me out pls!