2 weeks is a really, really safe bet. He's covering his ass.
When we pour concret, it's 7 days before we can drive on a standard mix.
Exactly.
Maybe 10 days depending.
I would also drill into the slab, like Dennis said 3-4 days. Hopefully the rebar was placed so you don't hit it with the bit.
I would be more worried about moisture under the safe than any strength issues. A slab on a slab has great lateral strength, it also bleeds out more on top because up is the only way for the moisture to go.
Of course you might as well wait the full 14 days just in case some freak thing happens later on with the slab.
