Originally Posted by
oldjackaroo
(2) there is a very obscure "Refund of numbered ticket 18750" with the number 18750 not corresponding to anything I can think about
Really? The 18750 is the miles refunded. As you posted, you transferred 53,000 miles and then used 52,500 for the upgrade that didn't happen leaving a balance of 500. Add 18,750 to it and you have the 19,250 which you said is your current mileage balance.