Fix BatchMemoryManager length

[dwahdany]

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] Docs change / refactoring / dependency upgrade

Motivation and Context / Related issue

Fixes #640 by ceiling the number of batches.

How Has This Been Tested (if it applies)

Checklist

• [x] The documentation is up-to-date with the changes I made.
• [x] I have read the CONTRIBUTING document and completed the CLA (see CONTRIBUTING).
• [x] All tests passed, and additional code has been covered with new tests.

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