easy. Assume 75% cases are EB2, the rest PERMs go to EB3 category. So, 4500 * 75% or 4500*25%.
Always do not forget the World EB2 are current so unused visas will be reallocated to China/India EB2s.
Always do not forget the World EB2 are current so unused visas will be reallocated to China/India EB2s.