Barbara - The site you have quoted is a commercial site. Those people have gone the the National Archives, copied and paid for the copying, then arranged the material in a logical way in an attempt to sell it. All of which is fine but probably the only way you will know just what they include under those descriptions is by asking them. If the work covers what you want it saves you a lot of work and maybe even some money.
When I was searching my husband's miltary history I took a chance remark he had made re a battle he had been in and found that there were two by the same name sort of. The first was not a real battle and the second was included in the Battle of the Bulge.My husband was in the first short "battle". I ordered and paid for a great many pages of info I did not want and could not use. And worse had to read all the way through!! That might be why you should see if the National Archive folks can help. Mary