The first value is the POI's orientation ("face north"), meaning you can put in values ranging from 0-3 at your leisure. The POI will or should spawn with its "front" in that direction (north, east, south, west). At this point, I can't tell you which number is for which direction, though, as I can't recall it at the moment. I read somewhere in this thread that Damocles made some changes to that mechanism, though. I don't know if that matters.
"y-offset" means the POI's height. You could, theoretically, also insert values at your leisure here, ranging from negative values to positive ones, but each POI should look / looks best when at its set default height. This means a POI was created (by an FP employee / a modder) with a certain default height in mind. And boy, finding out that correct default height can be a pain in the lower back.
When I create my lists or update them (https://github.com/NickPhaedra/7-Days-to-Die-NitroGen-Prefab-Lists/tree/Prefablists), I always cross-check each and every POI in the editor against its correct height or what seems to be the correct height to me (together with other values). The height value itself is in theory given in the POI's respective XML file, but this can be totally wrong when spawning it in NitroGen (although lately, most of the time the values actually check out to be alright when I cross-check them).
The x, y and z values describe the POI's dimensions in space (how "big" it will be when it spawns). I'd use the default values here (meaning the ones given in the POI's respective XML file; you can also check the default dimensions by loading the POI into the editor -> x,y,z values).
Hope this answered your question. Merry Christmas, and Cheers