sorting issue with csv.vim

gistfile1.txt

trans_count,trans_amount,portal_fee,sum
70,3.50,16.50,20
291,14.55,5.45,20
583,29.15,0,29.15
694,34.70,0,34.7
67,3.35,16.65,20
4431,132.93,0,132.93
142,7.10,12.90,20
379,18.95,1.05,20
22,1.10,18.90,20
8,0.40,19.60,20
27,1.35,18.65,20
121,6.05,13.95,20
3,0.15,19.85,20
487,24.35,0,24.35
2,0.10,19.90,20
486,24.30,0,24.3
416,20.80,0,20.8
5,0.25,19.75,20
732,36.60,0,36.6
761,38.05,0,38.05
264,13.20,6.80,20
161,8.05,11.95,20
40,2,18,20
77,3.85,16.15,20
1,0.05,19.95,20
62,3.10,16.90,20
135,6.75,13.25,20
7,0.35,19.65,20
548,27.40,0,27.4
21,1.05,18.95,20
701,35.05,0,35.05
468,23.40,0,23.4
432,21.60,0,21.6
351,17.55,2.45,20
1415,70.75,0,70.75
4,0.20,19.80,20
3,0.15,19.85,20
544,27.20,0,27.2
71,3.55,16.45,20
709,35.45,0,35.45
160,8,12,20
422,21.10,0,21.1
144,7.20,12.80,20
5043,151.29,0,151.29
542,27.10,0,27.1
798,39.90,0,39.9
405,20.25,0,20.25
14,0.70,19.30,20
109,5.45,14.55,20
340,17,3,20
525,26.25,0,26.25
513,25.65,0,25.65
5,0.25,19.75,20
11,0.55,19.45,20
17,0.85,19.15,20
731,36.55,0,36.55
334,16.70,3.30,20
1,0.05,19.95,20
3207,96.21,0,96.21
235,11.75,8.25,20
1187,59.35,0,59.35
519,25.95,0,25.95
371,18.55,1.45,20
2083,62.49,0,62.49
58,2.90,17.10,20
49,2.45,17.55,20
335,16.75,3.25,20
493,24.65,0,24.65
691,34.55,0,34.55
346,17.30,2.70,20
10,0.50,19.50,20
118,5.90,14.10,20
4,0.20,19.80,20
488,24.40,0,24.4
199,9.95,10.05,20
135,6.75,13.25,20
971,48.55,0,48.55
419,20.95,0,20.95
562,28.10,0,28.1
61,3.05,16.95,20
103,5.15,14.85,20
781,39.05,0,39.05
561,28.05,0,28.05
473,23.65,0,23.65
26,1.30,18.70,20
238,11.90,8.10,20
527,26.35,0,26.35
824,41.20,0,41.2
4,0.20,19.80,20
830,41.50,0,41.5
235,11.75,8.25,20
1249,62.45,0,62.45
599,29.95,0,29.95
226,11.30,8.70,20
384,19.20,0.80,20
5011,150.33,0,150.33
175,8.75,11.25,20
50,2.50,17.50,20
515,25.75,0,25.75
73,3.65,16.35,20
1,0.05,19.95,20
5,0.25,19.75,20
1,0.05,19.95,20
404,20.20,0,20.2
2584,77.52,0,77.52
1383,69.15,0,69.15
154,7.70,12.30,20
261,13.05,6.95,20
108,5.40,14.60,20
489,24.45,0,24.45
872,43.60,0,43.6
808,40.40,0,40.4
785,39.25,0,39.25
222,11.10,8.90,20
538,26.90,0,26.9
173,8.65,11.35,20
135,6.75,13.25,20
594,29.70,0,29.7
223,11.15,8.85,20
523,26.15,0,26.15
45,2.25,17.75,20
45,2.25,17.75,20
629,31.45,0,31.45
134,6.70,13.30,20
1339,66.95,0,66.95
1344,67.20,0,67.2
1735,52.05,0,52.05
654,32.70,0,32.7
2,0.10,19.90,20
71,3.55,16.45,20
723,36.15,0,36.15
157,7.85,12.15,20
542,27.10,0,27.1
493,24.65,0,24.65


:Sort! on the first column and you'll notice 971 appears first but on line 47 we have a total of 5043.

It appears the sorting is doing this: https://en.wikipedia.org/wiki/Lexicographical_order

see here: chrisbra/csv.vim#59