Hi Heidi
I think the declaration was sometimes required by the vicar/minister if the person (in this case the groom) was not known to him. I have a similar declaration on a couple of my early Australian certificates. I've only seen it on Australian records - someone else may know more about same.
If Elizabeth was older than her husband she may well have adjusted the numbers. My gg grandma married in Victoria in 1860 - she was 38, husband 30, but the marriage certificate said she was 34. Life was easier when no-one asked for "photo id" to prove your age
Trish