An expert is not necessarily a scientist:
"Brigadier Naeem Salik (retired) is a senior fellow at the Center for International Strategic Studies. Before his retirement from the Pakistani military, he served as director of arms control and disarmament affairs in the Strategic Plans Division, the secretariat of Pakistan’s National Command Authority."
He has served in SPD which is the agency responsible for protection of nuclear and strategic assets in Pakistan. It is reasonable to expect SPD officers to be well-informed about Pakistani nuclear matters on average.
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Production output depends upon what kind of warheads we are developing because HEU consumption will vary accordingly.
From the referred article:
"Pakistan’s capacity to produce HEU-based warheads is usually estimated to be about four weapons per year and, therefore, it could produce around 40 additional HEU-based warheads over the next decade. Currently, Pakistan has four operational plutonium production reactors at its Khushab complex. Assuming the reactors run at 60 percent capacity, each would produce slightly less than two weapons’ worth of plutonium per year, toward a total output of around 36 kilograms of plutonium—six warheads at 6 kilograms per warhead—per year. This suggests that Pakistan could produce up to 60 plutonium warheads over the next decade."
Big if still...
"Compared to the thousands of nuclear tests conducted by great powers during the Cold War, India and Pakistan have only conducted six tests each. Neither has enough data to develop highly sophisticated weapon designs requiring lesser amounts of fissile material. It is, therefore, highly unlikely that the estimated size of Indian or Pakistani arsenals comport with reality. Another problem is that these studies, while categorizing India’s entire substantial stockpile of HEU as potential fuel for India’s nuclear-powered submarines, do not address Pakistan’s future HEU needs for naval propulsion. Pakistan is striving to develop the naval leg of its nuclear triad, which would ultimately include naval vessels propelled by nuclear fuel."