Seems like Umfilter-Portion refers to the initial output sent to the reservoir.
http://www.kaffeevollautomaten.org/kaffeemaschinen/franke_br...
Nach Anwählen einer Brühstufe dosiert der Kaffeeautomat Heißwasser und Kaffeemehl in sein Brühgefäß. Nach Ablauf der Ziehzeit filtert er den frisch gebrühten Kaffee in sein Vorratsgefäß. Per Artikeltaste können Sie die gewünschte Ausgabemenge entnehmen.
...
Stufe 4,0 Liter, für kontinuierliches Brühen

https://www.coffee.org/Commercial-Coffee-Machines
You also want to factor in the brewing time when choosing the right commercial coffee machine, since you don't want people to waste valuable work time standing around waiting for the machine to finish another brewing cycle. In fact, you'll probably want to find a machine that has a large reservoir and a continuous brewing cycle so there's always fresh coffee waiting for your visitors and employees.

ttps://www.amazon.com/CoffeeSock...Filter.../dp/B00F8LVIYI

(2 Pack) Organic Cotton Cold Brew Coffee Filter Bag - Designed in California ..... brewed coffee to be poured through a secondary filter prior to consumption.

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Note added at 1 day 3 hrs (2018-09-05 02:42:52 GMT)
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espro.ca/esproblog/making-coffee-with-your-espro-press.html

19 nov. 2013 - Note that the SMALL ESPRO Press filter looks slightly different from this image, yet the design still uses a primary and secondary filter, ...

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Note added at 1 day 3 hrs (2018-09-05 02:44:01 GMT)
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to cover the "um"