Russ Hodgson

I am a new user to ASE, I thought I understood how the interpolation works (ish) but obviously I don't. My virtual aircraft is at the moment sitting at TKPK Robert L Bradshaw international in St Kitts in the Carribean the current METAR is, 190854Z 18000KT 10SM SCT092 26/22 Q1013 RMK ADVANCED INTERPOLATION. Now firstly this is a full metar report so why does it need interpolation? and secondly and the most odd thing when I click the interpolation details the reporting stations it is using is, NE Dist 1603 CWSA SE Dist 53 TAPA SW Dist 390 SVMG NW 51 TNCM. I can understand it using data from TAPA and TNCM but CWSA!!!!!! is 1603 miles away and SVMG is 390 miles away surely using data from these stations that are so far away can't be right can it? I might not be Michael Fish but I'm probably sure the weather on Sable Island is not quite the same as it is on St Kitts. If it is a case that ASE when using interpolation data looks for the nearest station in a straight line then surely there should be a limit to how far away it looks for the information. So is this a bug with ASe or have I misunderstood how the interpolation works?