set innodb_io_capacity_max=default unexpected result

MariaDB [(none)]> show global variables like '%capacity%';

+------------------------+-------+

| Variable_name          | Value |

+------------------------+-------+

| innodb_io_capacity     | 200   |

| innodb_io_capacity_max | 2000  |

+------------------------+-------+

2 rows in set (0.001 sec)

MariaDB [(none)]> set global innodb_io_capacity_max=10000, innodb_io_capacity=5000;

Query OK, 0 rows affected (0.000 sec)

MariaDB [(none)]> show global variables like '%capacity%';

+------------------------+-------+

| Variable_name          | Value |

+------------------------+-------+

| innodb_io_capacity     | 5000  |

| innodb_io_capacity_max | 10000 |

+------------------------+-------+

2 rows in set (0.001 sec)

MariaDB [(none)]> set global innodb_io_capacity=default, innodb_io_capacity_max=default;

Query OK, 0 rows affected (0.000 sec)

MariaDB [(none)]> show global variables like '%capacity%';

+------------------------+------------+

| Variable_name          | Value      |

+------------------------+------------+

| innodb_io_capacity     | 200        |

| innodb_io_capacity_max | 4294967295 |

+------------------------+------------+

2 rows in set (0.001 sec)