Yes it is one shot, prepare just what you need.
HOWEVER you can extend it by developing several films in one session (within a few hours)
There are instructions on the side of the bottle
I used to have 6 or 10 rolls ready to dev but I have only 2 tanks (2x35 or 1x120) but plenty of spirals.
So I used to prepare 1l of DDX 1+4 (200 ml)
then develop 1st tank, fix, and wash
then 2nd tank, fix and wash
for 3rd tank add 10% of original time, fix and wash
for 4th tank add 20% of original time, fix and wash
and so forth
That way it becomes cheaper and the results are very consistent.
You can always develop the most demanding film (fast) first and the slower later.
To DC Sang
Several years ago I had a discussion with D.carper from Ilford USA
DDX is definitlely NOT a liquid D76, but a product based on ILFORD DD (Dip and Dunk) developer.
It was aimed at home users who like to obtain the highest speed with small grain
From my limited experience it performs wonders with Delta 3200 and it is unbeatable for Neopan 400 and HP5. Delta400 gives good results, even though it is not my cup of tea.
Neopan 1600 works fine in this combo,
With slower films such as APX100, EFKE 100, Acros and others produces high quality image but the gain is less than in faster films. DDX can be used at 1+9 with no adverse effects.
SFX200 can give a long tonal range if developed 1+9 with ilford times.
I have no scanner unfoirtunately and the pcitures I have are photos of negatives inverted in the PC