Thanx for the good analysis.

In the conversion, the time should have been 22:24:38, not 22:24:37,
as the time in the LOG file is 222437.82, which rounds to 222438. Am

After 1.3.3, we added subsecond resolution to timestamps in both Magellan
and GPX formats.   With the development trunk, you'll get

It's in the development tree now and will be in the next (yet unscheduled) beta
or release we do.