Agilent Technologies X Series Manual page 115

If you enter a file name for a given file type, then the prefix becomes the filename you entered instead of
the default prefix, followed by an underscore. The last four letters (the suffix) are the 4-digit number.
For example, if you save a measurement results file as "fred.csv", then the next auto file name chosen for
a measurement results save will be fred_0000.csv.
Although 0000 is used in the example above, the number that is used is actually the
NOTE
current number in the Meas Results sequence, that is, the number that would have
been used if you had not entered your own file name.
.
If the filename you entered ends with _dddd, where d=any number, making it look
NOTE
just like an auto file name, then the next auto file name picks up where you left off
with the suffix being dddd + 1.
Key Path
Notes
Initial S/W Revision
Front-panel key
No remote command for this key specifically.
Prior to A.02.00
System Functions
Quick Save
115