Prepaid electricity questions

[Dumb and Dumber]

I only have prepaid two months or a bit less now, but I did see you don't get the same credits for your rands everytime.
For example if I buy only R50.00, I get 57 credits. But if I buy lets say R200.00 then I get only 190 credits. 4 times 57 is 228, not 190. Why is this happening?

Does the date of the month you buy tokens affect rates?
Does the time of the day you buy your credits affect the tarif?
Does the time of the day you enter your tokens into the meter affect the tarif?

I buy online at Prepaid24.co.za

Thanks

 

[Abu]

 

[xrapidx]

 

[Dumb and Dumber]

 

[Abu]

 

[tangmonster]

 

[THE MAN]

 

[Dumb and Dumber]

 

[tangmonster]

 

[THE MAN]

 

[Veedub]

 

[Dumb and Dumber]

 

[tangmonster]

 

[chrisc]