rom release numbering

Just a quick question about the release numbering. I was looking at other sites and sometimes (mostly) they have different release numbers. ex romulations lists 4937_-_Monster_Frenzy_(U)(SUXXORS) and an other site the release number will be 4991 - Monster Frenzy (USA). I thought this would be universal so what gives?
Thanks in advance

Most sites use different numbering for a variety of reasons. Our policy on not hosting DSi enhanced games was what made our numbers different among other things(bad dumps and the like).

there is no universal numbering system. release numbers are determined by the site and the site alone.