In a sales invoice template, you should allow users to easily add the column Unit separate from the Qty column. This is to align the item's unit in the same row and not under the Qty of an item.
Ideally Qty and Unit are in two separate columns and the corresponding value for the item's Qty and Unit should be in the same row. The Unit should not be added as a custom field since this is just a workaround. Unit value should automatically be displayed in the Unit column based from the Item's master data. refer to Chat transcript# #1354053