The synth level up estimates are not properly taking account the time required to synth an object when multiple ones are running. As an example if you are synthing something and only require one more completion to get the next level. If you have 2 synth slots making it and it takes 60 seconds to make the hover will show an estimated 30 seconds to next level even if both synth slots have over 30 seconds left.
I would have expected it to either show the minimum time needed to make that object or show the amount of time left before the next one completes instead of just dividing the time by the amount of synths making the object.