B-80 & the Ship's Code Card vs the Nav Gen answers

Hi Folks,
Studying Nav Gen at the moment and can not make these questions work out. As an example:
3 USCG #1019
You are preparing a weather report form, WS Form B-
80. The dry bulb thermometer reads 30°F (-1°), and
the wet bulb thermometer reads 28°F (-2°C). Using the
Ships Code Card, how would you encode the air
temperature groups in the report?

10011, 2003/

11300, 2124/

11011, 2124/

[B]11011, 2104/ [/B]the USCG answer…

D041NG

Using the Ship’s Card I get 11010, 81020 or if you make an assumption that the bulb is frozen (which is not stated in the question) 81020 becomes 82020…

Any in site would be appreciated!!
Thanks,
MTSKIER