It is possible to limit the minimum and maximum split of the subnet that you bring to the IP Address Market.
By default, the maximum split size is set to the block size of your subnet, while the minimum split size is set to /24.
This means that the customer can order any block size that you specify from your subnet.
If, for instance, you would like to avoid fragmentation of your IP address range, you can choose a larger minimum split size, like /18 - in such case. This way, it will only be possible to order a /18 or a larger block.
Similarly, if you would like to prohibit a certain maximum block size, you can specify this via maximum split size. For example, to avoid monetization of your whole IP address range, let's say - /16, you can configure maximum split size to /20 or lower.
Of course, it is possible to lease your entire block or only specified subnet mask of it. This can be done by selecting the same size in both fields.