We have a Kit type item that has 95 lines, so I just entered 11 of them to see what would happen.
Well, the first thing I realized is that there is a difference between "Lin" that prints (if so optioned) on the documents as Line Number, and for which there is one per parent item, and "Line #" as to how many actual lines of data there are on the SO.
After entering 11 items I was at "Lin" 11 and "Line #" 1045.
I'm not going to try and enter 1000 parent items to see what happens...