I uploaded two audio files into a sprite, one 4.7 mb and another 4.0 mb, and when I try saving the project, it says it cannot save because the size of media is over 10 mb, but this is wrong because 4.7 + 4.0 is less than 10, so can you fix this bug?
It's the total size of the saved project that is limited
If you export the project to your computer you'll see that the file size is over the limit.
Images and sounds are stored in the project XML as base64 so they take 30% more space.
I think Snap! should move to a better form of saving projects, like Scratch packages their projects as zip files
i agree with you
I honestly think this should be done at v11 or v12. I think that would be the greatest change to Snap!. Obviously, for compatibility, we should still allow people to save their projects as XML. 
yeah true, it makes more sense to drop something that big in like v11 or v12. it'd totally break stuff if we did it earlier lol. and yeah xml should definitely still be a thing—imagine not being able to open old projects 
This kind of change wouldn't mean that you can't open old projects in new Snap!, it would mean that you can't take a project from a newer version and open it in an older one (which already happens with new features). It would be kind of like Scratch - you can still take Scratch 1 and Scratch 2 projects and open them in Scratch 3.
You can actually open old BYOB .ypr files in Snap!, but only to an extent. Costumes are corrupted and the file just wont open under unknown conditions
I also don't know what a .ypr file is, but Google only says it's a BYOB save file
For me google says The .ypr file likely indicates a project file that contains all the necessary information about a project, such as task lists, resource allocation, schedule details, and other project-related data.