its not hard to guess it's about stress of words but what "ик-1, 2, 3" stands for? there is no explanation in my book about it.
ИК stands for интонационная конструкция (intonation construction), the numbers point at particular tone combinations:
"ИК" stands for "интонационная конструкция" (intonation structure) though I have to admit that this is not some wide-known term. It's just that some Russian-language linguists developed classification counting different intonations in Russian.
Here you can find one of such classifications.