Error message
In the message, %s marks a value that the engine fills in when it raises the error.
The story
Your script tried to show a value on the screen, and rush said it was too wide for the show window. Here is why that matters. Whenever you write a value, return it to the terminal, or drop it into a piece of text, rush turns it into text through one single door, and the result lands in a window of fixed size. Most values fit with room to spare. But a very large collection, or a very long text, can render wider than the window. The easy move would be to cut it off at the edge and print the first part. Rush refuses to do that, because a value that silently loses its tail is a lie on your terminal. You would read half an answer and believe it was whole. So it stops and tells you which door was showing the value, in the second slot of the message. Say you print a list of ten million items. The fix is to show less: take a slice, a count, or a summary, and print that instead. If you need the whole thing, write it to a holder, and read it back in pieces. Truth first, then convenience.
Text from the Rush engine's error catalogue.