Reserve fuel?

[Derek Daily <ddaily@SMTPGW.MITSUICOMTEK.COM>]

Background:
My VW owner's manual claims that my total fuel capacity is 18.5
gallons.  The next line breaks this figure down into two distinct
columns.  Column "A" states fuel capacity: 16.0 gallons.  Column "B"
states reserve fuel capacity: 2.5 gallons.
Question:  What is this 'reserve' capacity?  I have never been able
to pump more than 16.2 gallons into this thing.  I notice that the
regular Quant-m list total fuel capacity as :16.0 gallons.
I'm curious for explanations.  (Some of you may remember my question
about a tray in the back of the car.  I still think this may have
been used for an extra fuel container)
Gone for the weekend, I'll be waiting with bells for answers until
Tues.
SquirleyD
86 VW Qtm Syn
98 A4tqw -OR- 99 VW Pst Syn