Solved by MaazJamal in post #2 
              
              
                Nevermind I missed this part from the docs: 

stride  – the stride of the window. Default value is  kernel_size 

So the equation is (26+20-1(3-1)-1)/3 + 1 = 8 
and not (26+20-1(3-1)-1)/1 + 1 = 24 
The stride in denominator is 3 not 1. As is the case for conv2d layers.