Question about NPC's

[verenice]

As I understand each NPC awards 25 credits, and these credits can be collected twice a day.
Now my sister logged on to her account, which she hasn't been on since sometime before Christmas and when she collected the credits from the NPCs each one gave her 50 credits.
Is this because she hasn't collected credits for so long or did the amount of credits given change?

 

[Arnold]

I think it's a random chance that you'll log in and get 50 credits. I know sometimes during the week there's days where i'll just get 25 credits and then others when I randomly get 50.