It's not exactly a grammatical problem, but it's the closest match. The text reads, "Every day you get SuperBetter, you're having a positive impact on six people you know personally. They each pass on your strength to six people they know, and then they each pass it on to six more people they know. That's 256 people in total!"

That seemed off to me. So I did the math:

6 + 6^2 + 6^3 = 258

And that's not counting you! So add one more and you have 259.

Small math error, yes. But when a program has its roots in science, it's good to get the arithmetic right. Apologies for the nitpick, but I figured somebody might want to fix that.