Amos displays a happy face when the convergence statistic falls below the convergence criterion.
The convergence statistic cannot be smaller than 1 and should be close to 1. Gelman et al give the following rule of thumb. "...'near' 1 depends on the problem at hand; for most examples, values below 1.1 are acceptable, but for a final analysis in a critical problem, a higher level of precision may be required." (p. 297)
The default convergence criterion of 1.002 was chosen as a result of experience showing that it is quite conservative. The default value might be too stringent if the number of parameters is very large.