ANOVA and Tests of Linearity
The ANOVA table contains tests for the linear, nonlinear, and combined relationship between Age when first smoked a cigarette and # Cigarettes smoked per day past 30 days. The test for linearity has a significance value smaller than 0.05, indicating that there is a linear relationship between age and smoking level. The test for deviation from linearity also has a small significance value, which means that there is a nonlinear relationship in addition to the linear component. These results coincide with what you observed in the Means table, where age tended to decrease with increased smoking but the rate at which age decreased was highly inconsistent across smoking levels.