Question: Unit conversion problem?

This is my code - and I get the wrong output.... shouldnt it be around 900 K something?
restart:with(Units[Standard]):
T:=1200*Unit('degF');convert(T,'units','K');Units[UseSystem]('SI'):
evalf(%);
1200 Units:-Unit('degF')
2000
---- Units:-Unit('K')
3
666.6666667 Units:-Unit('K')
T:=1200*Unit('Fahrenheit');convert(T,'units','K');Units[UseSystem]('SI'):
evalf(%);
1200 Units:-Unit('degF')
2000
---- Units:-Unit('K')
3
666.6666667 Units:-Unit('K')
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