You can create new splits manually or edit some splits for the selected part manually. To enter new splits for the selected part, you will first need to uncheck the Auto Split column on the Large Parts page for that particular part. This in turn will enable the Edit split column button.
Now, when you will click this button, a dialog as shown below will appear.
In this dialog, the length of the part is shown along with it the required quantity is also displayed. You need to enter only the large piece length and the required split qty, small piece length is calculated automatically.
A part can be split in many different ways. All this splits will be considered only, if they satisfy the Joint Rules and that the quantity of split is not greater than the required quantity of the part. Both this conditions are checked when you click OK. If you click cancel, the changes you made won't be updated.
In the above picture, A part of length 9000 mm is split in 3 different ways, such that each of the split satisfies the rules and the split quantity is not greater than the required quantity.
The same splits are displayed in the split info grid on the Large Part Page.
The remaining quantity of the part that is not split is taken as it is and nested if possible.