Your disk is set up to use "sparse" storage, which expands the disk actually used as necessary, so yes, to prevent this happening in future installations, you should configure the disk to be fixed size at configuration time.
VirtualBox supports sparse disk images, in fact they are called "dynamic" images and are the default. Deleting a file makes no size to the disk actually used as VirtualBox is operating at the block level, while the file is deleted at the filesystem level - and when a delete is done, space is simply marked as unused - the space is not actually zeroed out and made reclaimable.
Depending on your usage case and requirements, it might make sense for you to separate the data and OS, and store the data on NFS for similar, such that you centralise and have control of disk space at the file level - at the expense of slower IO and more complex setup.