Don't put dashes in your flight number, that's nonsensical. But to be specific, the FMS Primer mentions only “Registration” (which has been renamed to "Airframe" on the generated flight plan page you screenshotted, Thanks SimBrief for being inconsistent) or “Fin Number” (which isn't displayed, but is from the selected airframe), nothing about "Flight Number" (which may still work if properly formatted, but I can't remember).