Incorrect time after the shift

[PalmtopTiger]

There is the line: Dialogue: 1,1:17:41.04,1:17:47.54,ED,,0,0,0,,sono mama no kimi ga sukidato

After shifting it back by 1045 ms it looks like this: Dialogue: 1,1:17:39.100,1:17:46.50,ED,,0,0,0,,sono mama no kimi ga sukidato

Look at the fractional part of the start time: 1:17:39.100. Should be 1:17:40.00.

The command i used: pysubs2.exe --shift-back 1045ms example.ass

Here is an example file: example.zip