I have a custom conversion set to trigger on our /thank-you page. I also have a Facebook standard event (“lead”) set to trigger on the same page. Interestingly enough, the numbers between the two rarely match. Often there will be a higher number of the standard event which gets me thinking. Does advanced matching only work with standard events? FB tells me that on some days it’s able to match twice as many conversions due to advanced matching.
I’ve tried checking if the pixel fires twice, but it doesn’t seem to be the case. So in a way the numbers seem legit enough.