A question please, regarding the Database Verification tool.

I currently have it set to :
Max no. of yrs between children = 8
Max span for all children = 25

It brought back a "large age differences between children" warning for a family where the children were born in
1862 (+1) 1863 (+3) 1866 (+1) 1867 (+2) 1869 (+4) 1873 (+4) 1877  (span = 15 yrs)

My question is, why?