The main risk of overdosing with Safe, or Prime, is 02 depletion. Obviously the result of overdosing will depend on each persons system based on numerous factors, such as water temp, pH, bioload, 02 levels prior and during water change, duration of water change, etc - along with how large of an overdose occurred - based on each individuals local water.
Impossible to sit on the sidelines from afar and guesstimate what the results will be with each member on this forum. Always best to crunch the numbers, and measure out an accurate amount for your personal needs based on your personal tanks. Nothing dramatic about using common sense.