I don't know where the hell did you get that, but I will try to explain to you, my dear skeptical friend, so you, too, can understand.
Look, from the start of row (4,3) start counting on the first square, count 4, space, and 3, as the indication says. Okay? Now, mark with a dot that last square. Now, on the same row but starting from the other side (in reverse) from the last square, count 4, space, 3. Where does the last square leave us? That's exactly right: On the same one that you counted before. So, no matter what you do, that SQUARE IS ALWAYS GONNA BE ONE WHERE YOU MUST MAKE A FILL. THERE'S NO ESCAPE, THAT SQUARE WHERE THE 3 COLLIDE, THERE GOES A FILL, NO MATTER WHAT. And from there, you can have a new hint.
That's one of many techniques that I use and developed from years of playing Picross.