Make the version formula for PRs in CLAUDE.md consistent with the pre-commit hook, which counts the commits before the new commit

CLAUDE.md

@@ -186,7 +186,7 @@ Each version section follows the v3.0.0 section of `NEWS.md`:
 
 ### Local commits on `main`: never touch the version number
 
-When committing directly on `main` in a local clone, **never** edit the `Version:` or `Date:` field in `DESCRIPTION`, nor line 1 of `NEWS.md`, and do not add a version prefix to the commit message. The git hooks in `.github/prehooks/` do this on every commit to `main`: `pre-commit` sets the version (commit count since the last tag + 9001) and date in `DESCRIPTION` and line 1 of `NEWS.md`, and `commit-msg` prepends `(vX.Y.Z.9NNN)` to the commit message. Adding NEWS bullets is still allowed. The section below applies only to PRs.
+When committing directly on `main` in a local clone, **never** edit the `Version:` or `Date:` field in `DESCRIPTION`, nor line 1 of `NEWS.md`, and do not add a version prefix to the commit message. The git hooks in `.github/prehooks/` do this on every commit to `main`: `pre-commit` sets the version (the number of commits since the last tag before the new commit, + 9001) and date in `DESCRIPTION` and line 1 of `NEWS.md`, and `commit-msg` prepends `(vX.Y.Z.9NNN)` to the commit message. Adding NEWS bullets is still allowed. The section below applies only to PRs.
 
 ### Version and date bump required for every PR
 
@@ -211,11 +211,11 @@ currenttagfull=$(git describe --tags --abbrev=0)
 defaultbranch=$(git branch | cut -c 3- | grep -E '^master$|^main$')
 git fetch origin ${defaultbranch} --quiet
 currentcommit=$(git rev-list --count ${currenttagfull}..origin/${defaultbranch})
-currentversion="${currenttag}.$((currentcommit + 9001 + 1))"
+currentversion="${currenttag}.$((currentcommit + 9001))"
 echo "$currentversion"
 ```
 
-The `+ 1` accounts for the fact that this PR's squash commit is not yet on the default branch. Set **both** of these files to the resulting version string (and only once per PR, even across multiple commits):
+This matches the `pre-commit` hook, which also counts the commits before the new one: the number of commits currently on the default branch + 9001 is the version of the next commit, i.e., of this PR's squash commit. Do not add 1. Set **both** of these files to the resulting version string (and only once per PR, even across multiple commits):
 
 1. **`DESCRIPTION`** — the `Version:` field
 2. **`NEWS.md`** — **only replace line 1** (the `# AMR <version>` heading) with the new version number; do **not** create a new section. `NEWS.md` is a **continuous log** for the entire current `x.y.z.9nnn` development series: all changes since the last stable release accumulate under that single heading. After updating line 1, add the new change to the appropriate sub-heading and group, following *NEWS.md style* above. If the change belongs to an existing group (e.g. `as.mo()`), add it there or amend the existing bullet instead of adding a new top-level bullet.