The Sub-codeis entirely managed by the application. During a creation, it is equal to 1 but can vary if the Fixed assets record is split into several lots, for instance, in the case of a transfer or a partial disposal (See the Splitsdocumentation).
In that case, the link between the original record (before split) and the Fixed assets record generated is "saved" via the first code, the sub code indentifying each of of there new record.
They are used as call numbers when searching a fixed asset record and when the function of fixed asset number management is carried out.