Can I upload several files at the same time?
Yes, this is possible, but the maximum size of a file is limited to 20 Mb and the total size of all files selected at once must not exceed 100 Mb.
Images that exceed 2000 px are automatically and proportionally reduced to this size during upload and then have a maximum size of 4 Mb. The order of the uploaded files can be changed later in Polaris.
You can find detailed information about this here.