Question about normalization constant Z_v1 and Z_v2 in the ContrastMemory

[YujieZheng99]

What an excellent work! I have learned so much from this paper.
But I have a question about normalization constant Z_v1 and Z_v2 in the ContrastMemory.
The Z_v1 and Z_v2 is initialized to -1，and Z_v1/Z_v2 is calculated based on out_v1/out_v2.
As shown in the following code， Z_v1/Z_v2 is updated only if Z_v1<0 and Z_v2<0，so Z_v1/Z_v2 will only be updated in the first batch.

if Z_v1 < 0:  
    self.params[2] = out_v1.mean() * outputSize  
    Z_v1 = self.params[2].clone().detach().item()  
    print("normalization constant Z_v1 is set to {:.1f}".format(Z_v1))  
if Z_v2 < 0:  
    self.params[3] = out_v2.mean() * outputSize  
    Z_v2 = self.params[3].clone().detach().item()  
    print("normalization constant Z_v2 is set to {:.1f}".format(Z_v2))  

But I think Z_v1 and Z_v2 should be updated in every batch.
What is your opinion on this，what are the benefits of this design?