Having just spent an age in maintenance mode tracking down a dodgy numeric field in a MASSIVE form, a simple suggestion for the Notes team is that if a numeric field is empty (i.e. in doc properties its value is ""), treat that as being the same as zero for the purposes of subsequent calculations and comparisons.
Notes is normally very forgiving re missing data, so I've never understood why it gets truculent with numbers.
If there are no plans to ever address this (emphasis added for the hard of reading), fine, at least give us error messages which indicate the problematic field / calculation: messages like "Comparison operators must be supplied two values of the same data type" don't cut it!!