Bug Report: You can calculate positive jumps in the timecode box, but not negative ones.
Eg, at 25fps:
If the timecode is 0:01:03:16 and you had to type +6:00, you'd be rightly taken to 0:01:09:16.
On the other hand, typing -6:00, leaves you with -0:00:06:00 in the timecode box.
To jump to a timecode value that is prior to the current time, type “+-” before the timecode value. This helps After Effects deal with the fact that you can have negative timecode values, i.e., you can place the Current Time Indicator before time 0:00:00:00. Layers and keyframes can also exist in negative time (ex., think about dragging a video layer to the left so that the first frame of your comp starts on the 1s mark of that layer).
There is detailed information here:
The way I think about “+” vs. “-” vs. “+-” in the Current Time field is this hierarchy:
1. Entering timecode without a + or – modifier takes you to that timecode.
2. Entering timecode with the – modifier takes you to the negative timecode value.
3. Entering timecode with the + modifier adds that value to the current time.
4. Entering timecode with the +- modifier subtracts that value from the current time.
I hope that’s helpful.