Hi Mike,
They would be using soda Ruby
When a 'gather' of soda Ruby is formed into a design, unless it is REHEATED it will not turn into Ruby but will be amber in colour ...........
The glass will only achieve its final color upon reheating the item in the glory hole. In its molten state, the glass resembles an amber color.
'Amberina' pieces being the result of the second heating being uneven.
Maybe a glass blower can explain it better.
Cheers,
Patrick.