System ID for custom line styles

What is the purpose of "System ID":

This property is accessed via the custom line styles:

Element Menu-Line Styles-Edit, then double-click on one of the custom line styles

We learned (the HARD WAY!!!) that somehow this box changed its number to something other than 0. When a number other than 0 is entered, the line style can not be chosen and the program will auto-select the line style to next style which is higher alphabetically that does NOT have a number assigned to "System ID".

So for the Bentley team - what is the purpose of this attribute? if it has no function, please remove it as entering numbers into it causes instability in line style selection.