Revert chunk size to 30x30.
Merge remote-tracking branch 'origin/139' into 139
fix PY-14453

(cherry picked from commit 00b2f01590bc90447c477b6a593aedc5de064567)
fix typo

(cherry picked from commit 234d5305929fb6d1c016be3b14f722a1740b511a)
revert erroneous change