To avoid buying the wrong product update or upgrade, be sure to double-check your existing license beforehand. Depending on the license management in use, please either open your eLicenser Control Center (old eLicenser-based) or the Steinberg Activation Manager (new Steinberg Licensing-based) and verify which license exactly is available in which version.
It might be possible that you have been upgraded to a higher version automatically (e.g. through a grace period), which would mean that you may purchase a smaller (and therefore less expensive) update or upgrade.