when u use the tng card, the reader will read the card and its remaining value, minus the charges and write back the new value

this info will be stored in the local database for eg: toll booth and will be uploaded by batch to tng main server

then the system will tally back the record with their current record and publish in the website for your transaction usage. thats why your current usgae of tng will no appear in the record after a few days

my opinion only