Just to be a little more precise, that last number 7 posted directly above was probably written with the intention of spurring us on to help the holy souls in Purgatory. There could be several exceptions where the indulgence gained is applicable to the holy souls only and not to the one gaining it. So far I know of one such exception, with it’s derivative partial indulgences; from the same Handbook of Indulgences :
From The Handbook of Indulgences, Norms And Grants
[1991 Catholic Book Publishing Company]:
**13. Coemeterii visitatio
Visiting a Cemetery **
An indulgence is granted the Christian faithful who devoutly visit a cemetery and pray, if only mentally, for the dead. This indulgence is applicable only to the souls in Purgatory. This indulgence is a plenary one from November 1 through November 8 and can be gained on each one of these days. On other days of the year this indulgence is a partial one.