I "blueprinted" concrete for my bots to place, much more then 601. The game keeps telling me it misses 601 objects, although it misses muuuuuuch more.
Laying down more blueprinted concrete doesn't add to the 601-counter. It seems that 601 is a magic number
Not a big issue, once the missing items go under 601 it does start to count right again.
IIRC it works like this:
-Factorio only tries to dispatch 1 construction bot to construct 1 ghost per tick
-After 10 seconds, the warning for failing to construct something disappears
-10 seconds * 60 ticks per second + 1 = 601 warnings maximum
You can also see that on the map. When you have that many ghosts only 601 warning icons appear on the map but constantly rotate through all the ghosts.