Interior window sills - What depth or overhang?

but not as agreed visible at 16 cm with 2.5 overhang, but at 18 cm with just under 4 cm overhang.

Your agreement was surely fixed in writing*, then that’s no problem, it just needs to be redone.

* I’ll gladly write an email in the evening after the phone call: "We agreed the following by phone today: ..."

And slowly I'm starting to feel like I should start drinking.

Drinking window sills beautifully will be expensive in the long run

Yes, I usually do that with the email too. This time as well, but there were many important points discussed that I did not go into the details of the windowsills. I also was not clear that something could go wrong again, which is actually impossible. The plasterers are already at work now, so I'll leave it like that. I can live with 4 cm. But I probably will never understand some things, sometimes I look for the hidden camera [emoji327]. But the proportional payment for that is off the table.