#15 Inconsistent parsing of hour values

[mark keenan]

One column of the spreadsheet contains 24 hour values "0:00" to "23:00". Getting the values works fine except for multiples of 6.

For example the first five rows "0:00" to "5:00" parse as expected, but the sixth one "6:00" is parsed as "0.25"

Likewise "7:00" to "11:00" parse as expected but "12:00" is parsed as "0.50"