That is one of the oddest things I have found after being raised in the country.
Whenever you ask an information to an Indonesian whom you do not know very well or whom you are not acquainted with, he/she would normally reply:
Oh, saya kurang tahu...
(Oh, I know less...)
What do they mean by "know less", really?
If a stranger happens to asks me the way to the nearest train station, there are only two choices of answer:
Sorry, I don't know (If I don't know the answer)
There is no such thing as "I know less", isn't there?
OK, let me see.... When you see that intersection over there, you turn right until you meet the FedEx building and...bla...bla.... (If I know the answer)
Such a bizzare thing we have here with the Indonesian language, but I guess it would take some time of getting used to for newcomers in this country to adapt to this kind of sugarcoatery of the local tongue.