How net amount calculate when Calculate tax automatically

F-02 Entry:

TAX rate: 8%

POSTK Account Amount 40 86120101 10 40 86120101 20 40 86120101 40 40 86120101 80 50 11110101 150

Simulate in GL:

POSTK Account Amount 40 86120101 9 40 86120101 19 40 86120101 37 40 86120101 74 50 11110101 150 40 TAX 13910101 11

TAX rate: 8%

M wondering how net amount calculate result is 9,19,37,74.......