Scanline sync functionality doesn't make any money and it is not a commercial thing. That's a hobby and feature, which I simply find interesting to develop in my free time and share with community.
The values provided there are incorrect. The purpose of scanline synchronization is to hide tearline inside vertical blanking interval. To achieve that you need to sync presentation to rasterizer position, located a few scanlines above the bottom of frame. Those few scanlines are required to render frame before it can be actually displayed. So for 1080p (with typical VTotal of 1125 scanlines) it should be somewhere inside 1125-delta range, where the delta depends on your GPU performance and application's 3D workload (read it as GPU rendering time). So there is no and won't be unified solution for everyone, you should tune it yourself for your specific system and your specific target 3D application. And yes, custom configuration can be required for each 3D application.
Also, context help for that feature in RTSS is explaining you how to interpret negative values. Positive values are explicit scanline indices, negative ones are translated to scanline index using index=VTotal-value formula. So for VTotal 1125, to start presentation lets say 25 scanlines before the end of frame you can specify 1100 and -25 to achieve exactly the same effect.
Everything regular user needs to know about scanline sync is reflected in the context help for that feature. Also I'm quite certain that I'm spending a lot of time daily (probably more than you spend on gaming ) on documenting everything in release notes and in the forum. But yes, I document things just once so new users need to use search a bit, if the question was already asked and answered before. Those who wish to find answers, can easily do it.