The radiation emitted by Cobalt 60 is essentially the same thing as an X-Ray but about 2 orders of magnitude more energetic. Simplified, if you are exposed to 1 second of Cobalt sourced gamma radiation that is going to be about the same as having an X-Ray source exposure over the same surface area for 100 seconds.
I had several treatments lasting several seconds each. It’s a bit hard to recall because I had just turned five.