Machine learning Wine Quality

Technical Discussions Python
#1

In this i am finding the correlation and alcohol is the highest correlated but after plotting the scatter plot it is showing weird type of graph as below .

End%20to%20End%20Project%20-%20Estimate%20wine%20quality%20_%20Automated%20hands-on_%20CloudxLab%20-%20Google%20Chrome%2014-04-2020%2017_26_50
End%20to%20End%20Project%20-%20Estimate%20wine%20quality%20_%20Automated%20hands-on_%20CloudxLab%20-%20Google%20Chrome%2014-04-2020%2017_26_501399×842 214 KB

Please HELP ME UNDERSTAND THIS HISTOGRAM