Click the dashed text in the Portions column of the row. The pop-up (its title literally reads "Edit categoryportions" in the current version) lists only the categories that row actually uses, each with a box per portion size and a live "X of N assigned" tally. For every category the portion counts must add up to that category's number of meals, or all be zero (use the default portion); otherwise saving fails with "Portion sizes for a category must add up to that category's number of meals (N)." Click Next, choose the apply-to option (including All new subscriptions and active subscriptions, which also updates open delivery dates that don't have meals selected yet) and Save. Only meal-prep portion sizes plus the default portion are offered — catering portions are excluded.