The platform allows uploading up to 30 images at once.
On IPHONE APP AND WEB
You can select each of the image and click DONE when you have selected all necessary images.
You will have to hold down to mark the first image, then select every other image after that. In other words, mark the first image by keeping finger on it for about one second, after which you will be allowed to select other images.
If you have any more questions, feel free to contact support.