Sequence Numbers start at '10' and increment by '10' for each line.
If you forget to add a sequence number, the line will be added to the end of the list.
Sequence numbers are changed on a router reload to reflect the increment by 10 policy (tip #1). If your ACL had numbers 10, 20, 30, 32, 40, 50, and 60 in it, on reload these numbers would become 10, 20, 30, 40, 50, 60, 70.
Sequence Numbers cannot be seen when using the Router#show run or Router#show start command. To see sequence numbers, use one of the following commands:
Router#show access-lists Router#show access-lists listname Router#show ip access-list Router#show ip access-list list name