Just did a
LIST MEMORY TO pubvars.txt noconsole

and there it was:

" 35 variables defined, 31 bytes used"

Obviously, some of the variables are using negative bytes; the more of such bytes they use, the more positive bytes are actually freed up. With some wiggling, one may use half the available memory in these negative bytes, and still have all the physical RAM free :).

There should be a professional memorial day, the in memory of the day when memory manufacturers went broke... over this finding.