When importing photos into Lightroom directly from an SD card, they are not numbered in the same sequence as they are on the card. Lightroom does not import them sequentially and assigns them numbers based on import sequence. This means that photos which need to stay together (HDR stacks for example) do not have sequential numbers. I can sort them by capture time in the software, but it is still confusing. Is there an option to force Lightroom to import them in the order they are on the card?
I don't think you can force a certain import order. I wouldn't be surprised if it actually starts multiple threads that do the import. I just always have the display order set for capture time.
Bob probably has you pointed in the right direction.
Regarding the sequence numbers, what are you doing with them that you cannot do with the file numbers?