It's best to keep app sizes as small as possible to preserve space on people's devices. All app projects have a 50MB limit, and free Thunkable accounts have a 200 MB total storage limit. If you need more storage fo your account then you can upgrade to PRO to get 1 GB of space for your projects.
You can view a project's app size on the project's details page:
The main contributor to an app's size are files (also known as assets). To add or delete files, click on the expand icon in the files section:
You can view your total account storage size in your account settings.
If you are near the limit, you may be able to create additional storage by removing projects that you no longer need like an old version or copy of a project. We may add the option for you to purchase additional storage in the future.