Well, Chloe checked his math, and then looked up at me with a mixture of pleasure and worry. She had found a mistake. Steven had quickly added up the numbers in his head, whereas Chloe had carefully worked out the addition on paper and she came up with a different answer. She re-checked it a couple of times to be sure before she pointed out his error.
Honestly, Steven was annoyed. He felt that she was a little too pleased with herself, and when she asked to see his paper the next time he didn't want to pass it to her. But he did. And now it has become a little tradition which amuses all of us, even Steve. Mostly their numbers agree. A few weeks ago Chloe's total was different than Steven's, but it turned out they'd both made a mistake on their first calculations.
A couple of weeks ago I documented the audit with my camera on my phone in Sacrament meeting. (Set to silent.) (Which was possibly still wrong to do.)
A funny brother-sister bond.