Is there an upper limit on the routing information that can be set for the subnet on the logical network?
There is a limit when setting with the GUI (up to 4 lines).
If you try to set more than 5 lines, the creation/editing of the subnet fails due to an error. (Error message: "Maximum length of static route exceeded")
Reference: Tutorial - Logical Network - Subnet Details
On the other hand, there is no upper limit when setting with API.
To set routing information of 5 lines or more, please execute it with API.
Reference: API Reference - Subnet