The "A" array provided in the question will result in a dimensions mismatch error. I'm assuming A is an [nx2] char array.
A = ['KM'; 'KL'; 'MN'; 'KM'; 'MM'; 'KL'];
% Convert char array to cell array of strings
Acell = cellstr(A);
% Find groups of strings
[groups, groupID]= findgroups(Acell(:));
% Count members of each group
count = sum(groups(:).' == unique(groups(:)),2);
% Display results in a table
countTable = table(groupID(:),count(:),'VariableNames',{'Group','Count'});
Result
countTable =
4×2 table
Group Count
_____ _____
'KL' 2
'KM' 2
'MM' 1
'MN' 1
