It's 5 attachments per post. There are two ways you can add additional pictures to your post:
1. Upload your pictures to a hosting site, then insert the image via URL and uncheck the 'reference locally' box. This doesn't count as any attachment on your post, so you can have as many as you want.
2. You can make separate posts when you advance in the goals, similar to how you made the first one, with attachments. Then, you can get their URLs (click on the attachment to preview, right-click, copy image address) and add them to your first post using the same instructions as above
You would still only get 5 attachments per post you make, but no limit to how many images you could store on your first post.
I'm not sure how easy either would be to do from a phone, but I hope that helped
Thank you again for keeping us updated!