What's the difference between the "balance" and "highest balance"?

These fields show up on the Debt Details page

The "balance" field refers to your current statement balance. The "high balance" can be your current balance too if you're just getting started. It can also be used to track existing payoff progress before signing up on the site. For example, let's say you have a credit card with a current balance of $1,000, but it got as high as $5,000 last year. You've been paying it down in the meantime and the current balance is down to $1,000. The high balance would be the $5,000 number. However, if you want to start the progress from scratch, just use your current balance as the high balance too. The highest balance is only used to track your overall payoff progress percentage.