The “training zone” is just zones for TSB.
At a high level, TSB is really just comparing your current amount of training with your amount of training recently. In this case, “amount of training” is measuring in TSS (which is basically difficulty-adjusted hours), “current” is an average with a span of roughly a week, and “recent” is an average with a span of roughly six weeks.
The occasional long weekend rides, which are high TSS, spike your averages up above the level of the prescribed training plan. When you follow the plan for a week, it’s necessarily “gray zone” material, because your recent average has been pulled up by the high-TSS event.
Specifically, your outdoor ride on 2/29 put you 200 TSS over the plan. The following rest week dragged you up to the grey zone. The first couple of weeks of SSB2 are a little friendly, so with the residual boost from the outdoor ride, you’re oscillating around in the grey zone for now instead of oscillating around at the top of the green zone.
What I would do is not worry about it.
I’ll note also that the outdoor rides may be particularly high TSS, perhaps because you’re using a different power source that reads higher than your indoor trainer, or because your performance indoors isn’t as high as outdoors (and your FTP is set from an indoor test). You have a 4-hour outdoor ride with 0.9 IF, which is pretty high.