After verifying OLMIS-6156, it turned out that there is currently no indication in the Quantity field that the value is too large.
Instead, after trying to save the changes, the correct message appears.
Log in as administrator and go to Administration > Products.
Click the Edit button next to any product and go to the Kit Unpack List tab.
Add product, enter too large value (e.g.11111111111111111111111) and click the Save Kit Unpack List button.
Notification appears that the Kit Unpack LIst couldn't be updated, but the field with Quantity isn't marked in red.
The "Quantity" field should be marked in red with an exclamation mark (as e.g. in the requisition product grid) and on hover of it, a popover with the following information should appear: "This number is larger than what can be saved".