Hi Garry,

from the help:
If the Shell function successfully executes the named file,
it returns the task ID of the started program.
Which doesn't help you much...

I'm not sure what these numbers represent but whatever the values are they
do not appear to be appended to the file.

No, for appending use "".
Then you don't have to worry at all,
about "open for", "close", "write", whatsoever.