[jhv48]

The bushings limit how many degrees the timing advances. I believe the black bushing is 18 degrees. The springs limit how fast or slow the timing advances as you rev the engine (lighter springs, faster advance). The initial timing is set by you at idle. So, 16 degrees initial timing plus 18 degrees added from the black bushing nets you 34 degrees total. The springs control at what rpm that total advance is reached.

Clear as mud, right?