Error message
In the message, %s marks a value that the engine fills in when it raises the error.
The story
You gave a process a priority that rush does not offer. Here is the idea. Every process in rush runs in slices of time called quanta. The strip is how big a slice that process gets, as a percent of the base quantum. And there are exactly three choices: twenty-five, fifty, or one hundred percent. That makes slices of about six, twelve, or twenty-five milliseconds. Why only three? Fewer points means the slices of different processes are more likely to line up, which keeps the scheduler simple. So what about a strip of twenty, or seventy-five, or zero? Refused. Rush does not round to the nearest point, because silently turning twenty into twenty-five would be deciding for you. And the refusal happens before the process is born, so nothing is left behind, no thread, no id, no heap. One more rule: a child never gets a bigger strip than its parent. Ask for one hundred under a parent at fifty, and the child is born at fifty. The fix is easy: pick twenty-five, fifty or one hundred. The message shows the value you wrote. Choose a point, and the process is born.
Text from the Rush engine's error catalogue.