doc: update doc for mixed:N batch size #7567

Job	Run time
Build source distribution	19s
determine-arm64-runner	1s
Build wheels for cp311-manylinux_x86_64	5m 27s
Build wheels for cp311-manylinux_x86_64	6m 24s
Build wheels for cp311-macosx_x86_64	6m 9s
Build wheels for cp311-macosx_arm64	3m 32s
Build wheels for cp311-win_amd64	6m 48s
Build wheels for cp310-manylinux_aarch64	5m 59s
build_pypi_index	13s
build_docker (12)	2m 31s
build_docker (_cu11, 11)	2m 32s
upload_pypi	0s
deploy_pypi_index	0s
Pass testing build wheels	1s
	39m 56s

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