What is the significance of the test?

Brookfield viscosity is measured in Centipoise (cP), which is absolute viscosity

Absolute viscosity (cP)= Kinematic viscosity (cSt) X Specific Gravity

The Brookfield apparatus uses a rotating spindle, the torque applied is measured and determines the viscosity
This type of apparatus works particularly well for low temperature testing

As Badenewsbare correctly states Brookfield is usually a low temperature viscosity measurement, almost entirely used on new oil to confirm the SAE W viscosity
rating. Also on ATFs (Dexron/Mercon) to confirm max viscosity requirements at the stated temerature(-40C)
Low tempearture performance is affected by pour point/VI
and base fluid selection.
A lab would generally not conduct a Brookfield on used oil because of solids contamination damaging the equipment.

In my country the lower ampient temperture is 10 ,should iworry about Brookfield and CCS viscosity