In order to delete a photo from your timelapse, please go to your timelapse tab, click the specific photo you'd like to delete. In iOS, there should be a little white square icon with a pencil in the bottom right corner of the screen. It will open the picture. There will be a trash icon on the bottom right hand corner of the screen. To edit, click the "Edit" option on the top right hand corner of the screen.
In Android, click the pencil icon in the upper righthand corner. This will open up the image. Proceed to click the trash icon in the upper right hand corner.