The shelf life plot shows the change in the response over time. The plot also shows the estimated shelf life.
If batch is a random factor or is not included in the final model, then Minitab displays a single plot that shows all batches. If batch is a fixed factor and is included in the final model, then you can specify how many batches to show on the combined plot and whether to show individual plots for each batch.
Plots for individual batches show the shelf life for the specific batch. Combined plots show the overall shelf life.