Royals fleet numbering

[arrifirststage]

I have asked before but maybe everyone is as confused as me..........can anyone explain the royals fleet numbering system.
I realise that 10xxx,20xxx,30xxx,40xxx are used to signify coaches,single deck and double deck according to length.What I cannot follow is the apparently random numbers within these blocks with for example Darts,Solos etc seemingly jumbled up.

[Liverpool Street]

Rotalas fleet numbering system is a thing of urban legend. Some say the numericals are in order, others say they sould start again, and what is common belief is that no one uses the numbers of which are on the vehicle, and just go by the last 3 digits of the registration plate...

In other words, its too damn confusing to follow their fleet

[4747]

Rotalas fleet numbering system is a thing of urban legend. Some say the numericals are in order, others say they sould start again, and what is common belief is that no one uses the numbers of which are on the vehicle, and just go by the last 3 digits of the registration plate...

In other words, its too damn confusing to follow their fleet

that may be the case at LAC with regard to reg numbers but Tividale use fleet numbers. The Royals themselves are sequential 30821-30828