When petitions, Efforts, and Landing Pages are created in the toolset they don't have specific signature goals. Instead, the signature goal is updated based on the number of signatures that have been received. (When a petition is first created, it has a goal of 100 signatures. When it reaches 100 signatures the goal is updated to 200 signatures, etc.)
However, if you want a petition, Effort, or Landing Page to aim for a set number of signatures, you can set a custom signature goal.
For petitions, this can be set by going to the petition > Admin > Admin Settings > Petition Page section. From here, enter the signature goal into Custom Goal of Petition Signatures.
This will update the progress bar to reflect the new goal.
For Landing Pages and Efforts, the signature goal can be set by going to the admin homepage > Efforts (or Pages) > name of your Effort (or Landing Page) > Settings > Homepage Content Section. Then enter the signature goal into the Custom Goal of Petition Signatures box.
Keep in mind that if you want visitors to see the signature goal, you'll also need to check the box labeled Show Progress Bar. If this box is not checked, the progress bar – with your updated signature goal – will not be displayed.
Once the custom signature goal is met, it will revert to default behavior (meaning that the goal will be updated incrementally as signature thresholds are met).