I 130 - why the uscis processing time is moving backward?

I am a green card holder i filed for my husband my priority date is oct 02 2019
I want to know why the uscis processing time is moving backward ?
When i saw it was on july 30 for california service center and thn all for sudden it move back to 27 june and now its on may 27 can you please help why its going like this ?

Dont worry , USCIS immediately jump to next priority date at once

just like it is coming back , it will jump in a one go

My Priority date jumps from december to march 2020

So have some patience due pandemic close Backlogs are creating , so it will take some time

Thank you soo much @pprabhjott
But how we will get to know whats the actual status.
My concrn is before it was showing processing time 8 to 12 months and now its 10.5 months to soo on …