csvsort confusion

gistfile1.txt

$cat small.test | csvsort -c 1

1.0000000000000,vex,vex
-0.31829694255,vex,did not by
-0.162250196859,vex,had
-0.0233508789385,vex,first brought
0.0212758403934,vex,was
0.0212758403934,vex,was
0.0212758403934,vex,was
0.0367116830716,vex,was a man of
0.0416822192964,vex,was on
0.0670064083637,vex,first sat in

testdata

1.0000000000000,vex,vex
-0.162250196859,vex,had
0.0212758403934,vex,was
-0.31829694255,vex,did not by
0.0212758403934,vex,was
-0.0233508789385,vex,first brought
0.0416822192964,vex,was on
0.0670064083637,vex,first sat in
0.0367116830716,vex,was a man of
0.0212758403934,vex,was