There is one difference between the image produced by the tutorial above, and the image provided in the link, and that is that the image provided in the link has a few extra configurations added.
Especially the configurations from
Most interestingly for you probably is the added:
# Real life SD cards typically have less than they advertise. First off, they # often use a base of 1000 instead of 1024, and even then they are often smaller # than advertised. The number below is based on a conservative target of 7.9GB # (that's mathematical GB, base 1000), converted to MiB, rounding down. MENDER_STORAGE_TOTAL_SIZE_MB=7534