Amos 1:3 ASV, Amos 1:6 ASV, Amos 1:9 ASV, Amos 1:11 ASV and Amos 1:13 ASV

I'm still trying to understand the intended meaning behind the phrase used here: "For three sins of ..., even for four, I will not turn back my wrath." The contemporary English version uses the phrase "for countless crimes". The Lord maybe saying: "even after ignoring 3 sins, nay even 4 sins, I will not turn back my wrath". Or is he saying perhaps, "because of 3 sins, even because of 4 sins?". Or is he saying, "to gain 3 sin, even 4 sins". To me it is unclear, but I suspect "even after ignoring..." maybe the best interpretation. All that being said the actual meaning seems to be insignificant. The major theme here is that God is angry and he will not let these injustices to his people go unpunished.