With release 5.8 of the DCR portal we introduced a new business rule, the pre-condition rule, which combined the condition and milestone rule into one common rule. For business people there is mostly no reason to distinct between these three different rules, so the pre-condition rule should be mostly used, where condition and milestone can mostly be ignored.
If you start a simulation and renders the process model you will see an image like this:
You can also check out the expense report model found here. If you Fillout Expense, Approve then you can payout.
If you now Reject you cannot Payout anymore:
The reason is the milestone rule, the purple rule next to the condition rule.