Standard practice nowadays is to include both. Though what isn't so standard, with Manga Ent. in particular, is wether the English subtitles are a relatively direct translation or instead, the script of the English dub - the latter being cheaper as it means having only one script to have reviewed by the BBFC but defeating some of the advantages of subbing (specifically, not needing to fit mouth movements nor be extra-Americanised, supposedly to sound more natural when spoken aloud, and other such changes).
As a rule, never pay any attention to Amazon's product details. Look for images of the back of the box or check the distributor's Web site. Looking at the entry on Manga Ent.'s own site for this box set it clearly has: LANGUAGES Japanese English SUBTITLE English