When submitting my meter readings, what do I need to put in the night rate box?

I’m on a single rate electric meter. When submitting my meter readings, what do I need to put in the night rate box? It won’t let me continue with nothing in it

You need to contact Bulb directly on Monday. They obviously have you logged as having a two-rate meter when you actually have only a single rate meter. They need to change the details on your account. Once that is done, the website will ask for only one reading.