Iran has some of the most sophisticated missile systems out there. Defense systems are alway playing catchup, so I do not doubt that they could easily overwhelm "Israel's" countermeasures. They could probably level everything if they wanted to, but seem to be focused on solely military targets for the time being.

Could they be inflating their numbers to make themselves look better? Yes probably, most every government would do the same and I am sure anywhere there is a range of damage they are going to err on the high side of their estimates. But it isn't a stretch to assume that a country that has basically built their entire defensive doctrine around the ability to missile strike anywhere with extreme efficacy is able to do exactly that. This is basically Iran's area of expertise.