^Looks something like that. The actual data are the numbers, with the ‘#’ added (with inverse coloring b/w fg and bg colors) and my shell newlined. This is an intended zsh feature, not a problem.
PROMPT_SP Attempt to preserve a partial line (i.e. a line that did not end with a newline) that would otherwise be covered up by the command prompt due to the PROMPT_CR option. This works by outputting some cursor-control characters, including a series of spaces, that should make the terminal wrap to the next line when a partial line is present (note that this is only successful if your terminal has automatic margins, which is typical). When a partial line is preserved, by default you will see an inverse+bold character at the end of the partial line: a “%” for a normal user or a “#” for root. If set, the shell parameter PROMPT_EOL_MARK can be used to customize how the end of partial lines are shown. NOTE: if the PROMPT_CR option is not set, enabling this option will have no effect. This option is on by default.