Normally, this would be Q541 & this train, if it's running about what it normally runs, would be working Cartersville in the afternoon/early evening. However, due to sitting in Etowah most of the previous night, it was reassigned to X541. There are two reasons I can think of as to why Jacksonville came to that decision. The first one being to it running out of it's normal time slot. The second, & more likely reason, is because by changing it to an extra, it won't affect performance & dwell time metrics, which are some key talking points that in the age of PSR, can affect the all mighty share value of the company. All Hail Wall Street!