Co-worker asked for a call and then when I replied "you can call when ready :) " the reply back is an all caps "IN A MIN"

I'm not the one asking for the call and I'm also not rushing you to have one.

To me all caps means shouting and it puzzles me because while typing it the other person can see it and previous that they aren't using all caps. Why continue using all caps if you aren't angry? 🤷

How do you interpret all caps in a work chat conversation?