Would you be able to share more with regards to the status field in those ADS-B records ?
I've done some research and the message as you described does not seem to be a standard S-record so your supplier seem to use some custom format.
There is even more to it than that, as this particular flight, flight WN1747 from Milwauki to phoenix @ June 19th, seem to have some particularities (but perhaps that is why you choose to use this flight as an example)
This flight was scheduled to depart from Milwaukee at 19 jun 20:20 UTC (15:10 CDT), but in fact departured at 15:14 CDT (4 minutes late)
This flight was scheduled to arrive at Phoenix at 19 jun 23:50 UTC (16:50 MST), but in fact arrived at 16:42 MST (8 minutes early).
The (EPOCH) timestamp of the S-Record message is 19 jun 23:44, thus recorded two minutes past arrival.
There are about 20 additional data points but nothing that I can use.
So you say. No reason to doubt that statement but I do wonder.
Because your supplier seem to have a mind of its own about what should and shouldn't be part of those records, things could become messy.
Right now it looks more to me that your supplier witholds (vital) information either because a) your supplier hasn't got those informations to begin with and/or b) attempts to squeeze you out for even more money in case you do wish to obtain the actual information.