Where did you see those recommendations? I was debating changing my manual trans. fluid too but I didn't see any data supporting a change one way or the other - Blackstone didn't have enough data either to tell me whether it was necessary.
At any rate, the filling capacity is 1.6 Liters. Note that the instructions say to fill until overflowing, which in my experience is typical for a manual transmission fluid change:
https://www.newtis.info/tisv2/a/en/f...box/1VnXyO2l8u