I think the problem with your calculation is you are using the APR as a monthly calculation amount rather than a yearly amount. The A (annual) PR is the amount that you will be paid over the course of a year on a balance. 31 cents is accurate.
Your average daily balance was obviously more than $6000 because you never took any money out. The average daily balance was less than $9000, because that is your balance now. So, lets just assume it was in the middle at $7500.
$7500 * .0005 = $3.75
$3.75 / 12 = 0.3125 or 31 cents.
Thank you for posting in the Community. ChiefCz is correct. We take your average daily balance and multiply by the annual percentage yield (APY). The resulting value is divided by 365 (days in a year) and then multiplied by the number of days in the cycle (month). Using this calculation, the distribution of interest appears to be correct.
If you would still like to speak with someone regarding this matter, please reach back out to let us know.
Thanks for your help in addressing the question!