I find problem with Wingate 6.01
Traffic records in log files of www proxy service indicates 0, but really that must be normal numbers.
Example from log file:
0000031181 Requested http://img.yandex.ru/i/i-announce2.gif
0000031181 Traffic 0 0 0 0 0s
About 2/3 records have that problem. Accordingly Billing program incorrectly show statistic.
At the same time, on user page accounting traffic calculation is really true.