Hello,
I am also trying to use the time dilation tool for a supermassive black hole, specifically, TON 618, which has approximately 66 Billion solar masses. However. I continue to get imaginary numbers. Here is the rundown:



So this gives us a horizon radius of 1.949x10^14 m, or 1.949x10^11 km
Converting to g, this gives us 23.515 g (doesn't this seem really low?)
Entering these figures, I keep getting imaginary numbers. Does I make a mistake somewhere along the line? Thanks in advance.