In a mass spectrum, how can the sum of relative abundances be greater than 100?
2.3:10, 23:100 and (23/123):(100/123) are all correct values for the ratio of the relative abundance of B-10 to B-11.  However, only the last value, (23/123):(100/123) or 18.7:81.3 shows the normalized ratio of relative abundance of these isotopes.  It is this normalized value that adds up to 100.