Improving numerosity skills using magnetic fields?
Your title is pretty misleading. The rather strong magnetic field used to inhibit an area of the brain in this study might help understand how the deficits in a savant's brain lead to unusual abilities in very limited areas, but it isn't anything that could be considered practically for improving numerosity.
Do you have some specific question related to the article?
I saw this on NGC channel too. It didn't look too impractical. Just 15 minutes of exposure to a strong pulsating magnetic field and the effect will last up to an hour.
Separate names with a comma.