I think he is asking why the -250ish isn't 50% of the -350 line since the probability is ~50/50 once you get to OT. Basic explanation would be that the odds are still in your favor that the Dutch win in regulation meaning you win the bet.
Look at it this way, you have the PK line for 90 (-350) which pushes on a draw and the 3 way line (-140) which loses on a draw after 90. If you now throw in the entirety of the game, with draw not a possibility (to advance play), that line has to be somewhere in the middle of the 3 way and the PK line. In theory a 50/50 would split the 210 difference between the 350 and 140, for 105, or -245. That is how you get the to advance line, it is basically splitting the difference between the PK and 3 way line.