Prepaid Electricity Suspicious Activity

This evening I purchased 2 prepaid electricity vouchers via the capitec banking app.I bought the first prepaid voucher for R400 and recieved confirmation of my purchase and the mention of my total units which amounted to 219.6kWh. I then proceeded to purchase the second voucher,also for R400 but recieved confirmation with units that amounted to 132.1kWh. I'm utterly disturbed by this as the difference in units is really significant (87,6kWh). I would need to get a thorough explanation of this kind of magic because wow, it's ridiculous. I don't normally take note of the units and rand value but after today, I am convinced that this is ********** and very shady of the bank. Where did my units go?