RAW
The Combat Rules concerning Splash Weapons go as follows:
If you miss the target (whether aiming at a creature or a grid intersection), roll 1d8. This determines the misdirection of the throw, with 1 falling short (off-target in a straight line toward the thrower), and 2 through 8 rotating around the target creature or grid intersection in a clockwise direction. Then, count a number of squares in the indicated direction equal to the range increment of the throw. After you determine where the weapon landed, it deals splash damage to all creatures in that square and in all adjacent squares.
Illustration given by d20pfsrd.com is:
What I understand
If the X in the above picture misses its target "T", and then roles a 1 on a 1d8, she will hit herself(count a number of squares in the indicated direction equal to the range increment of the throw)
My problem with that
This seem to me as overly harsh to splash weapon users (like Alchemists). Like all ranged attackers, there is a miss chance (a bit lower because vs Touch AC), but if she misses (even without fumbling) there is a 1/8 chance to damage herself AND other ranged party members standing beside her.
Did I just misread? Is there a difference between "range" and "range increment"? How should this be interpreted?
Best Answer
I think you misunderstood (but the wording is kinda confusing)
The example that your image comes from does not use the range increment to count squares, but the number of range increments thrown. This gives a very different number, as it means the distance by which you are off depends on the total distance thrown and you'll never hit yourself.
So in the case of the example, with a 25ft throw and a 20ft range increment, what you would do is determine the number of range increments thrown (which is 2, since you're outside the first range increment of 20ft and into the second) and then count that many squares. That means your bomb would fall 10ft short of the mark, a long way off from you.
It also means that the further you try to throw your weapon, the further off from the mark you'll be if you miss.
I'm fairly sure "the number of range increments" is also what they mean in the normal rules, although it's written in a confusing fashion.
Note that with your reading, you could even throw backwards, which is possible if you try to hit something within 10ft of yourself with a 20ft range increment bomb, and that makes no sense at all.