an arrow means that a number divides exactly into another number ('is a factor of')
in this work it needs to be fairly often repeated that all the arrows that can be drawn have been drawn
so you cannot have a number that divides into another without there being an arrow to show this
start off with students drawing the arrows themselves:
draw all the arrows that you can to show the relationship 'is a factor of'
for this reason, you should not use 1 or the number itself