Digit sequence has wrong length

The fully-formatted error message

The digits for the 'year', '199', has the wrong length: '3'.

          199-05-29?12:25:12.1-01:00 
          ^^^

A 'year' requires 4 digits.

Substitutions

Name	Value	Type	Source
Input	199-05-29?12:25:12.1-01:00	String	The ISO8601 string being parsed
Expected	4	Int	What the parse command is looking for
Actual	3	Int	What the parse found
PreviousName	Nothing	Nothing	In this example, the error field is the first one
PreviousValue	Nothing	Nothing	The value of the immediately preceding field
PreviousType	Nothing	Nothing	"digits" or "delimiter"
PreviousStartOffset	1	Int	The displacement from the start of the string being parsed to locate the leftmost '^'
PreviousCharCount	3	Int	The number of '^' chars to position under the previous value
TopLine	"The ? for the '?', '?', has the wrong length: '?':"	String	This error category
BottomLine	"A '?' requires ? digits."	String	This error category

Notes

1. The Value column above describes the example values in the sample error message above.
2. The offset of the actual error position is calculated: it is always after the sum of the PreviousStartOffset and the PreviousCharCount.
3. Here's an example where the number of 'X' is zero. Conflicts with Required delimiter is missing.
4. Note that TopLine and BottomLine have '?' marking where values will be substituted.
5. I'm wondering if the type of the preceding field can be automatically derived.