[Koha] dewey class and subclass etc

can anyone explain how should i fill up information in adding a new item? like the Dewey, Dewey sub class what is this? When we tried, we keyed in '005' and '133' accordingly but when c searched for the said book what we saw on the Dewey info was 5.133, why? what does the 'Number' indicate? another is the grouping, what is this for? i havent seen a entry for the said grouping.. How can u edit the data that you entered? im confused while finding a way to do this. and also after searching for items, does the system display the call card no, author no etc? pls help!