How is InstanceSelection set on a report model based on a OLAP cube ?

When autogenerating a report model from an OLAP cube, what is the criteria used by the SQL engine for deciding whether the InstanceSelection tag should be List or DropDown. As far as I can see, this decission is pure magic.

E.g.

<Entity ID="udm:Entity_Dimension_Person_Ulykke_Arbeidsoperasjon">

<Name>Person Ulykke Arbeidsoperasjon</Name>

<InstanceSelection>List</InstanceSelection>

<Entity ID="udm:Entity_Dimension_Person_Ulykke_Stilling">

<Name>Person Ulykke Stilling</Name>

<InstanceSelection>Dropdown</InstanceSelection>

I would have anticipated that both these two attributes should have been List, but as shown, one is List and the other is DropDown.

I have a hunch that the choice is made on basis of the EstimatedCount attribute of the dimension attribute, but if so, what ranges are used to indicate which value

In this case the EstimatedCount for all attributes are as follows:

Arbeidsoperasjon 142
Fartoytype 184
Fartsomrade 44
Fiskerimerke 254
GeografiskOmrade 107
Legemsdel 38
Miljoskadetype 30
Personulykketype 38
Stilling 85
Ulykkessted 62
Utstyr 123

Somehow, it seems that

Below 100 -> DropDown

Above 100 -> List

But, this does not hold true for FartoyType with an estimated count of 184 so my guess is

Can someone confirm this and give the exact range

Trond