This article explains how Spectrum get the values to calculate and generate this alarm.
Spectrum 10.4.x
The attributes and OID's used are the following ones:
ciscoMemoryPoolUsed (0x210a60) - 1.3.6.1.4.1.9.9.48.1.1.1.5
ciscoMemoryPoolFree (0x210a61) - 1.3.6.1.4.1.9.9.48.1.1.1.6
Those attributes are not located in the device model, but in the Cisco_Mem_App application model: