First, this is not assembly.
It means shift the content of ret 10 positions to the left and place it back in ret. Shifting left actually is multiplying by 2 (in this case 10 times resulting in multiplying by 2^10 (which equals 1024)). So if ret contained 1, it now contains 1024.
Similarly, shifting right is the same as dividing by 2.
There is a programming
section here on LQ which might be a better place for programming related questions. Just for the next time that you have a similar question.