Thanks for asking, David!
It’s myth busting #3:

However, as a reader you don’t have to think about this. Medium wants you to clap for what you like. If you like everything equally — sure give everyone 1 clap or 50 claps, it doesn’t matter.

As a reader, if you give 50 claps to things you don’t like, it makes it difficult for you to reward things you do like. Don’t do this.

So, basically clap as you would in real life — love something, shower it with claps! Think something was good or okay — a few claps! Something sucked — don’t clap.