Downloading additional content needs extra space in Logic Pro X and MainStage 3
You can select items to download in the Additional Content window in Logic Pro X and MainStage 3. When you do, you may notice that the amount of space needed for the installation listed at the bottom of the window is larger than the size of the downloads you select to install.
This is normal since the installer needs storage beyond the size of the downloads that you install. The total space that's needed to perform the installation is shown at the bottom of the window. However, once the download is finished, the amount of space used will be the the size of just the downloads, not the larger number shown at the bottom of the window.