Think this is new today, almost all events show no numbers inside the coloured pen circles, even though clicking on an event shows 5+ in at least one pen.
For example, 1545 GMT today Evo race details shows ~30+ signups ZwiftPower - Login
But the schedule list shows nobody has signed up. ZwiftPower - Login
This was Google Chrome on pc, now looks resolved.
I find that the little circles don’t truly represent actual signups. I want to say that they only show riders registered on Zwiftpower, as looking at the same events in Companion often show bigger numbers. The signups also only update periodically, so there could be a delay before Zwiftpower shows the real numbers. It doesn’t seem consistent. 
Yeah, it’s incredibly frustrating when you sign up for a race as a Zwiftpower user, there’s only a few minutes before the race starts and you have no idea how many of the total signups on Companion app are late Zwiftpower user signups… Are there 5+ Zwiftpower riders in the race, so (the IMO poor) Zwiftpower ranking and (much better IMO) ZwiftRacing.app ranking changes can take place?