Trying to understand my electric bill

Hi, when I send in a reading for electric, I have to put the same reading i.e 8155 in 2 boxes or it won’t let me send it.
Why are there a day and night rate?
How can my night use be more than my daily use?
Does everyone have a day and night rate?
Have I been paying twice?

My meter is a smart meter which was already fitted by British Gas when we moved in last year which gives me a total reading, but I put this in twice when submitting a self-reading.
Thanks

Meter readings (Day)
25 August 2018 8155 Estimate
25 September
2018
8473 Estimate
Meter readings (Night)
25 August 2018 8128 Estimate
25 September
2018
8545 Estimate
Energy (day) 319 kWh @ 13.30 p/kWh £ 42.40
Energy (night) 417 kWh @ 13.30 p/kWh £ 55.45

Standing charge 31 days @ 23.39 p/day £ 7.25
Dual fuel discount 31 days @ £ 14.29/year - £ 1.21
Cost of electricity used £ 103.89
VAT @ 5% £ 5.19
Total electricity costs for this bill £ 109.08

Hi there @Tony870 thanks for getting in touch. It sounds like the issue here might be that your meter does in fact have two readings, and it isn’t displaying both of them to you. In that case, you may be able to get both readings out of the meter (this page will hopefully help: http://support.bulb.co.uk/customer/portal/articles/2805466-how-do-i-read-my-meter-) and we’ll need both of them, or alternatively the details we have for the meter are incorrect and we think that there are two readings when there’s actually only one. If you can’t get a second reading out of the meter with the instructions on that page, then is there any chance you could email a picture of the meter to help@bulb.co.uk? Then I’m sure we’ll be able to get our details updated if there is only one reading.