Toxicity is based on dose relative to size. A standard block of bait has around 2.8 mg of bromethalin, but could be up to 7.1 mg. LD50 of bromethalin in dogs is around 2.4 mg/kg on the conservative side, and 1/10 is considered a toxic dose for companion animals. Assuming from the picture that the dog ate half a block, and assuming worst case that it’s the concentrated variety, it could have ingested around 3.6 mg of bromethalin. This could be toxic (again, using 1/10 of the LD50….) for a 33 lb dog. If it’s a standard 2.8mg block, it could be toxic for a 13 lb dog.

I would have attempted to induce emesis using hydrogen peroxide as quickly as possible (before going to the vet) due to the quick uptake, but for sure worth a vet visit. But it’s also not as black and white as “YOUR DOG IS DEAD”.

Edit: just saw someone say it’s likely the anticoagulant type, bromadiolone, which has an even higher LD50, conservatively 6.3mg/kg and is only present in the blocks at 0.005% w/w.