Once you have generated your required sizes from your Master layouts, you can begin to edit them independently. You might find that you only need to fine-tune some sizes, or you may decide to make more significant changes to one or more sizes.
Ad Sizes can be edited in the same way as the Master layouts. Elements can be added, edited or deleted from an individual size by clicking on the appropriate thumbnail in the Ad Sizes Control Column.
Once you have made changes to an Ad Size, clicking on ‘Generate’ will overwrite those changes. If, for some reason, you need to go back to change the Master Layouts, you can prevent the changes from affecting a given size by clicking on the Ad Settings cog under the Image thumbnail and clicking the ‘Ignore Regeneration’ checkbox.