Fix subsampled size

[mloubout]

Subsampled size is incorrect. Number of points is div(size, factor) + 1 because div(size, factor) is the number of intervals notnumber of points

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.67%. Comparing base (29fecdc) to head (c12b994).
⚠️ Report is 3 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff             @@
##           master     #230       +/-   ##
===========================================
- Coverage   97.60%   85.67%   -11.93%     
===========================================
  Files           3        3               
  Lines         792      789        -3     
===========================================
- Hits          773      676       -97     
- Misses         19      113       +94     

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[jkwashbourne-oss]

Thanks for the fix!