Because each ad is run with a unique group of respondents, you may be limited in the number of ads allowed in a single project.
For self-serve projects, the number of ads you can include in set up depends on the target sample you have requested. Once your requested sample is made available to you, you will see a note regarding the maximum number of ads that can be tested using that sample:
If you would like to test more than the maximum number of ads allowed in a project, you can create additional projects for any remaining ads. Please note that this can cause longer fieldwork times.