For example: After sequential numbers, #120-125 has been created you can click on the text box (once it's selected) click on Copy / Paste and the same information will be duplicated on the same label it was created on:

For example: If you paste the sequential numbers / letters into the 3rd label - the sequential set up will still start on the original label it was created on.
When creating or using the copy /paste features for sequential numbers, edit all must be selected.