Urgent reassurance needed

I have migrated on phone from Income Support ESA and Support Group to Universal Credit it's confirmed to LCWRA and my first payment is April 23 here is where I am concerned,I received my fortnights (2 weeks) run on but ESA sent me a letter saying claim ended but say they sent me 68 pound? Where has that come from what's concerning me is I know the run on won't be deducted off my universal credit but what about this? Will it be seen as an overpayment so thus deducted? Tried everywhere but nothing puts my mind at ease,I know it's not a huge amount I know it's well trivial really but all that's happening recently has got to me and my health so please cansomeone help PLEASE?