File numbers in ContactsLaw are a concatenation of the client number (of the primary client), a full-stop (.) and then a number indicating the sequence in which the file was opened, relative to those that preceded and succeeded it.
It is important to note that file numbers are not decimal numbers, therefore file "300.1" is not the same as file "300.10".
Files for subsidiary companies are prefixed with an additional code to identify the company to which they belong, e.g. XYZ.1.1