Why is there an extra (4) in the output of align?

documentclass {article}  

usepackage {amsmath}  
usepackage {amssymb}  


begin {document}  

With `` align* ''  ( you require manual numbering) :-  

begin {align*}  
alpha &= beta + gamma                                      quad  quad quad quad quad quad quad quad (1)   
alpha + beta &= frac {gamma}{delta}   + delta int mu dmu         quad quad quad quad quad (2)   
alpha + betamu &= gammadelta       quad  quad quad quad quad quad quad quad quad (3) 
end {align*}  
  
  
  
  
With ``align'' (you get automatic numbering) :-  

begin {align}  
alpha &= beta + gamma   
alpha + beta &= frac {gamma}{delta}   + delta int mu dmu    
alpha + betamu &= gammadelta  
end {align}  
end {document}