How monitoring BW for period of time ! not all the time

[mixmox]

Hello
trigger:
net.if.total[ens192,bytes]
will monitor usage bw of device which count total bw that device used since network adapter turns on,
i cant filter the amount of bw for 1 month,

i want to know amount of bw that used by device per month not all the time,
i have such these data from other monitoring system like cacti and prtg, they show bw per month
any idea ?