As you build a recipe you see a list of ingredients on the screen.
To access the option to pick which ingredients are % labelled use the drop down arrow to make the extra fields visible.
To choose the characterising ingredients tick the "Show Ingredient %" option.
This will cause the % of the ingredient to display next to the text in the Declaration field.
If you choose the "Show Group %" option Zubi will display % of all ingredients with the same text in the Declaration field as well as showing a % for any compound declarations related to the ingredient.
This is useful if you have ingredients you want to group, eg. fruit, vegetables, spices etc, and for which you may also want to declare the individual ingredients.
NOTE: The Show % option will not work for Ingredients classified as Additives. It would be very unlikely you would declare the % for an additive as it is not characterising.
The % displayed are round to the nearest whole number if >5% and to the nearest 0.5% if less than 5%.