A Factorio mod that lets you type or scroll to select an exact number of items.
Ctrl+1 then Ctrl+2 (like typing '12' with Ctrl held down) to select 12 items of the stack held in your cursor.
Ctrl+mouse wheel to 'scroll' up or down one item at a time.
Ctrl+R to recall a stack (item type, quantity) like the last one you manually selected.
More stuff/other increments can be found in Factorio's "Controls" screen when the mod is loaded.
The core method is the control.lua apply_desired_grab function.