Update manual.md

[dmbates]

Spelling correction

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.89%. Comparing base (3712291) to head (30a36fe).
Report is 23 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #539      +/-   ##
==========================================
- Coverage   87.43%   85.89%   -1.55%     
==========================================
  Files          26       27       +1     
  Lines        3288     3395     +107     
==========================================
+ Hits         2875     2916      +41     
- Misses        413      479      +66     

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[quinnj]

Thanks @dmbates!