What is the difference between "inode size" and "Bytes per inode"

Below information is taken from man page,I would like to know the difference between bytes-per-inode and Inode-size?

-i bytes-per-inode

Specify the bytes/inode ratio. mke2fs creates an inode for every bytes-per-inode bytes of space on the disk. The larger the bytes-per-inode ratio, the fewer inodes will be created. This value generally shouldn't be smaller than the blocksize of the filesystem, since then too many inodes will be made.Be warned that is not possible to expand the number of inodes on a filesystem after it is created, so be careful deciding the correct value for this parameter.

-I inode-size

Specify the size of each inode in bytes.mke2fs creates 256-byte inodes by default. In kernels after 2.6.10 and some earlier vendor kernels it is possible to utilize inodes larger than 128 bytes to store extended attributes for improved performance.The inode-size value must be a power of 2 larger or equal to 128.The larger the inode-size the more space the inode table will consume, and this reduces the usable space in the filesystem and can also negatively impact performance.Extended attributes stored in large inodes are not visible with older kernels, and such filesystems will not be mountable with 2.4 kernels at all.It is not possible to change this value after the filesystem is created.