The arrows indicate that you multiply each one, that way you don't forget in the long run, especially once you get to multistep algebraic equation.
So first you multiply the -7y by the 4 and you get -28y, if you remember a negative times a positive is a negative (I like to think of it as bad things that happen to good people is a bad thing ;) ) Now you take the -7y, because you have to multiply it by both numbers in the parenthesis, and multiply it to the -y, and since when you multiply two y's together it becomes squared it is 7y^2 (squared) and since both are negative, they cancel out and become a positive (bad things that happen to bad people is a good thing in a sense) So therefore your answer for the equivalence is 7y^2 + -28y
Hope that helped, my math teacher has a lot of tricks for remembering this stuff :)
