When travelling on German DB trains with a seat reservation, you usually get a car number and a seat number. Seat numbers are integers unique within each car.
Typically, these seat numbers are distributed in a somewhat sequential manner from one end of the car to the other. However, I am saying somewhat because it has happened more than once to me that I missed a given seat at first. Within each row or pair of rows, seat numbers seem to be distributed according to a pattern that I do not quite understand yet.
To illustrate this, here is a partial screenshot of the seating scheme from an IC car that can be accessed while booking a train ticket on bahn.de:
When looking at seat numbers in such a schematic view, it looks like seats are always numbered in groups of eight (i.e. across two adjacent rows), adhering to the following schema:
5 6 7 4 3 8 1 2
Now, when standing in the aisle in the middle of seats, that schema does not become quite as apparent (thus leading to some confusion when searching for one's seat, especially when subject to limited mobility due to luggage, children, or other passengers in the aisle). Is there anything to avoid about numbers ending in 9 or 0 so they do not appear based upon this schema? And anyway, I wonder whether there is any system behind distributing the numbers within such a block of eight seats.
What is the reason or benefit behind this way of numbering seats?
EDIT: While there seem to be a couple of numbering schemes, my impression is that at least "normal" IC and ICE trains feature the numbering as described above. Thus, I would like to exclude any additional numbering schemes from yet other train types from the focus of this question, although other special cases that I did not cover here and that do appear on IC or ICE trains (e.g. unaligned tables, maybe) are still within scope of the question.