Priority level with Cortex-M

Hello,

How can I set Polyspace (Code Prover) to modelize IT's priorities behavior of a Cortex-M processor? I mean that in the Cortex-M processor, some priority has a level of interrupt greater than other interrup. Thus, if a lower priority is handle, this one can be interrupt with a higher priority. But the reverse is not allow; the higher priority will never been interrupt by the lower priority.

In the Polyspace (Code Prover) setting panel (Configuration -> Multitasking -> Interrupts), there is a green arrow to move-up or down the interrupt. What is the goal of this green arrow?

Thanks in advance. Best Regards