The GE Slimline KeySafe can use up to 7 digits, giving 10 million
possible combinations.

Does it really allow you to use the same digit more than once? And
distinguish the order in which the keys are pressed? The few I've ever
used don't.

But I've assumed that the main consideration is that the majority of
burglars looking for their next fix don't have the patience and/or short
term memory to work through the combinations.

--
R