Quicky create a new file using dd

dd if=/dev/zero of=myfile bs=1G count=0 seek=5

This will create a 5GB file called myfile. Notice the count=0 and seek=... commands. Just seek the size you need. ls -l should show the correct size. I hear that sometimes Linux can’t fully recognize the size until the file is used. If that is the case try file myfile.