What is the meaning of the ''minus number'' (-3) after the Facebook ID in my profile's page code (''InitialChatFriendsList'')?

0,2,3 are chat status codes. Regarding your second question of the order in which they are sorted, this order is determined on many factors and basically depends on the frequency of mutual interaction between you and the person available at that Facebook id. This mutual interaction depends on your chats, comments, likes, profile visits, page visits, etc. The comments pose a good question. I think, the 3 status codes for each individual is present to calculate the "Seen at" and "Active ago" or "Idle since" times. There is very little on no information about this on the internet and on Facebook Help as well and I think it makes sense because all these may be a part of Facebook's algorithms which might be their trade secrets as well.

These two links delve into the arcane mysteries of the FB numbering system in much greater detail.  :-) http://mashable.com/2014/02/05/facebook-id-number-what-it-means/