A fast way to know that the process is too detailed is when participants in the room start to discuss decision nodes. For example, if Yes, this is what happens, but if it’s No, then this happens. Decision nodes are typically too detailed for a SIPOC.
Another fast way to know is when there are more than 8 process steps. In this case, start grouping like process steps together and ask the group to re-name that set of activities into a higher level activity.
Lastly, a strategy to use is to tell people to envision themselves on a plane and they’re looking at the process at 10,000 feet high. The cars, buildings and trees are pretty small!