Number of dropdown items with TWebEditAutoComplete

In the demo given by TMS the number of visible countries is limited by a scrollable dropdown list. However, in my application the the number of visible items is not limited and excites the application boundary.
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You can also go to Caribbean plant species distribution and add for example 'a' in the edit box.
Any idea how to make the list scrollable? In the TMS demo I haven't detect any species css code.

Set WebEditAutoComplete.PopupHeight to the max. height you want to allow.

But strange enough the TMS demo provides this functionality

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Set WebEditAutoComplete.PopupHeight to the max. height you want to allow.