Can't upload worlds to Realms

When uploading my singleplayer worlds I get hit with an error message instantly of “Upload failed! (group id 1426686647" is too big C7 2097151 2 Use STAR or POSIM extensions to overcome this limits” and another error message when I try and create a new world through the realm configure screen with a seed.

Can there please be a way to upload worlds through a web interface?? Thank you!