microSD card's between manufactures vary way to much (even between
lots), for
BeagleBoard.org we eventually settled on 85% of stated
size.
dd if=/dev/zero of="${media}" bs=1024 count=0 seek=$((1024 * (GB_SIZE * 850)))
been using that default for a few years now.
Regards,
--
Robert Nelson
https://rcn-ee.com/