“Righto, See You Then.” Means “Okay, See You Then”

“Righto” is an informal Australian response meaning “okay”, “understood” or “let’s do that”. It can answer a proposed arrangement or acknowledge an instruction. Here, right is not an adjective meaning “correct”; righto functions as a complete response, usually with a brisk, friendly tone.

For example: “Meet outside the station at six?” “Righto, see you then.” In a formal email, Okay or Certainly is usually safer. Righto is distinctly conversational and can sometimes sound slightly playful or old-fashioned. Its main job is not to express enthusiastic approval, but to confirm that you have understood and accepted what happens next.

https://dictionary.cambridge.org/dictionary/english/righto
https://www.collinsdictionary.com/dictionary/english/righto