p. 50

Power Saving Mode (PSM)
Setting AT command ”AT+CPSMS=1” can be enable the PSM mode. In this mode, The mode is similar to power-off. But the module remains registered on the network and there is no need to re-attach or re-establish the network connections. And all of the functions will be unavailable except the RTC function. PWRKEY and timer expires can wake up the module.

p. 53

PSM supply current: PSM mode Typical: 9 uA

there is also a hint on p. 23

IVBAT(power-off) Module power current in power off mode:
Min. – / Typ. – / Max. 7 uA