I think many of us don't start purging until an hour or more after the 2nd dose of Epsom Salts in the morning. Remember that your intestine is miles long so it takes time for the whatever is in you to travel all that distance. With me the grapefruit starts to come out -( I can see the small pink grapefruit cells) just before and during the time the gall stones start coming out and that's about 4pm or later. What comes out first will be the digested food from your last meal and it may be a formed or partly formed stool. Once that is cleared out of your gut the Epsom Salts works more efficiently to attract water into your large intestine so that the rest of what's in your gut comes out more rapidly.
Clark did write that older peple are more likely to be deficient in magnesium.
Some people don't pass stones until the next day when they come out with the digested food from whatever they ate in the evening after the purge. There were several messages in the past few weeks on this forum where people described their experiences with the flush and when they start purging.