I think there was a systemic problem when some data was indexed
I have been using the data from "Canada, Ontario, Toronto Trust Cemeteries". I have noticed that some of the people are listed as 0 years when their tombstones show them to be 70 or80. The problem seems to stem from the age being listed with the number of months. e.g. 80 years and 6 months. Here are some names from the Toronto Necropolis Cemetery.
Robert Peters (1891)
Ann Peters (1887)
Thomas Robinson (1887)