meaning expression

[marcohadiyanto]

hi,

i'm new for using qlikview and found this expression.

avg({$<perYear = {$(=max(perYear))}, perMonth = {"<=$(=max({<perYear={$(=max(perYear))}>} perMonth))>$(=max({<perYear={$(=max(perYear))}>} perMonth)-1)"}>} OD_Days)

i don't understand. anyone can help me?

thanks before.