Have you not got a copy of the bills posted to your apartment or registered online with Iberdrola to get copies emailed to you?
Charges are on a daily basis so may depend when the reading was made.
For most, the standing charge is 37 cents a day (45 cents inc. 21% IVA) and electric used worked out at 16 cents per kw (19.5 cents inc. 21% IVA). Plus meter hire charges etc.