On top of what has already been said (607 B.C.E. is a made up year that is entirely contrary to the voluminous evidence) the WT states that a "prophetic year" (as in the 2,520 days) is 360 days, yet they arbitrarily switch to 365 day years to arrive at 1914. Their own crazy talk is internally inconsistent.
That is a point I have made before also. There is just NO WAY they can make their numbers add up...