That's all it says!
The Staff records are simply the Staff Books:
Names, type of job, DoB, Date entered service, Rates of Pay - just as I mentioned.
You haven't updated your profile, so it's impossible to know where in the world you are, and what Ancestry subscription you may have?
But, if you go to Search, and Card Catalogue; enter Railway as a search term - UK Railway Employment records come up as the first item?
Then entering William Henry Thomas Prout will bring up those 2 entries I mentioned.
You may need to contact Swindon Library, or get someone to search the relevant records at TNA.