Actual usage of the word "Dryly"

dry adv. dry′ly, dri′ly TFD

• Devoid of bias or personal concern: 'presented a dry critique'

  a. Lacking tenderness, warmth, or involvement; severe: 'The actor gave a dry reading of the lines'. b. Matter-of-fact or indifferent in manner: 'rattled off the facts in a dry mechanical tone'.

  13. Wearisome; dull: 'a dry lecture filled with trivial details'.
  14. Humorous in an understated or unemotional way: 'dry wit'.

From internet sources, I got to know that this word is used when we are being funny but actually are serious.

I think the main point is that you are missing something very important: the person says something that is funny, but they say it in a way that makes it sound serious.

It's not about whether what they say is funny or not, but about how they say it, or the delivery.

I can't imagine that.

Imagine someone tells you that they ate rice with a spoon, and you pretend to be very serious when you tell them I prefer my rice with vegetables. That could be seen as dry humor.