Dev: Writes "this feature will take some time..." (proceeds to list bullet points touching on the main modifications required)

Manager: Can you explain what you mean by "takes some time?"

Dev: ...

Manager: ...

Dev: As I mentioned in the past, and this is pretty technical.... you use that thing between your ears only to prevent the top of your head from falling off.

just respond with the screenshot of your previous message with a thick red rectangle around the bulletpoints with a big red arrow pointing to the rectangle with big bold red text at the arrow saying "this was and still is the explanation"

Well, "some time" in itself doesn't mean anything. How long is that? 1 minute, 10 minutes, 10000 minutes?

Be exact! "This will take approximately 7 work-days" :D

@lankku Almost everyone who has done development knows that 90% of non-trivial jobs involve solving as yet unknown problems. You also find out pretty quickly that many managers think that's no impediment to setting a time frame for completion.