Here’s the detailed version of what happens. As the token is created, it checks the printed values of the Myr Propagator it’s copying — or, if the Myr Propagator whose ability was activated was itself a token, the original characteristics of that token as stated by the effect that put it onto the battlefield — as well as any copy effects that have been applied to it. It won’t copy counters on the Myr Propagator, nor will it copy other effects that have changed Myr Propagator’s power, toughness, types, color, or so on.