Electricity bill in sector 10

I shifted in a shared 2bhk flat in sector 10 during starting of July. On 2nd August my flatmate shared electricity bill of 10k asking me to shared half of it. During start of my stay she said the bills are for 2 months' usage..but now she says this current bill is for 1 month only. Can this happen? Mostly I have heard that EB in faridabad comes for 2 months. Pls help clarify!

P.S.: I am out off faridabad and am planning to ask her for actual bill copy when I'm back next week.