I am planning on planting a series of 7 letterboxes in my area in the next couple of days

The fact that you're planting these boxes over a couple of days suggests that the boxes are spread out over a wide area, and you might be better off listing the boxes individually.

Keep in mind that there are two distinctly different types of "series" as far as letterboxing is concerned. One is a group of boxes planted in close proximity that you expect people to find in a single outing. The second is a bunch of boxes spread out over a wide area that share a similar theme. (Such as a series planted along the 45th parallel or the Continental Divide).

As far as Atlas Quest is concerned, that second definition does not exist. A series on Atlas Quest means the boxes are in close proximity and you expect people to find them all in a single outing, and that's it.

If you're hiding a series based on a theme spread out all over a city or county, you should probably list them separately.

-- Ryan