Interpreting negative value in varImp () random forest

I am using a function randomForest()

from the randomForest package. I am trying to understand the output given by the varImp()

caret package function . It shows negative values ​​for several variables. What does a negative value indicate?

Below is the result:

           Overall
Year        6.7712260
Month      -2.6684553
DOW         2.2681865
City.Group -0.3534247
Type        1.4049568
P1          8.5207072
P2          6.0449333
P3          5.3579060
P4          4.1441309
P5          5.9207454
P6          7.3744485
P7          3.6858546

      

        
        
        
      

    

Thanks in advance!