Why isn't this double for penalty?

[slar]

http://www.bridgebase.com/tools/handviewer.html?sn=slar&s=SA82HAQT9DJT7CQT5&wn=Robot&w=SKQ965H653DAQ4C86&nn=Robot&n=SJT73H4D9653CA974&en=Robot&e=S4HKJ872DK82CKJ32&d=e&v=n&b=2&a=1H(Major%20suit%20opening%20--%205+%20%21H%3B%2011-21%20HCP%3B%2012-22%20total%20points)P1S(One%20over%20one%20--%204+%20%21S%3B%206+%20total%20points)P2C(Opener%20two%20rebid%20--%204+%20%21C%3B%204-%20%21D%3B%205+%20%21H%3B%203-%20%21S%3B%2011-16%20HCP%3B%2012-18%20total%20points)P3H(Correct%20back%20--%203+%20%21H%3B%204+%20%21S%3B%2010-12%20total%20points)PPD(16-%20total%20points)P4D(4+%20%21D%3B%2020-%20total%20points)PPP&p=S4S8SQS3C8C4CKC5C3CTC6C7D7DAD3D8SKS7D2S2C2CQD4C9S9STDKSACJDJH3CADTDQD5H2S6SJH8H9&c=6

 

http://tinyurl.com/j4bhzyh

 

I passed twice and the opponents invited. I have a trump stack and my double is alerted as 16- points. In many instances GiB will alert a double as takeout, even when the level is quite high. For the most part I've learned to sit back and take my plus in these cases. However, this time there was no indication that GiB would take out the double (especially with a mere 4 cards) so I went ahead and tried it. Well, GiB took it out anyway and turned +300 into -400. (Sure, I could have declared differently but it was still a bottom either way.)

 

If I can't trust GiB's explanations, the game is very difficult and frustrating to play.