Fix aiter context len mem frac setting.

[saienduri]

Motivation

This PR is to fix the discrepancy in this cleanup PR: #12136

Modifications

Accuracy Tests

Benchmarking and Profiling

Checklist

• Format your code according to the Format code with pre-commit.
• Add unit tests according to the Run and add unit tests.
• Update documentation according to Write documentations.
• Provide accuracy and speed benchmark results according to Test the accuracy and Benchmark the speed.

[Fridge003]

Covered by #12137