If the user does not specify a NodeId, newly created nodes receive their NodeId directly from the UaModeler. This is done to prevent the user from keeping the used identifiers. By default each node class has “its own” range of numeric NodeIds, i.e. beginning from a numeric identifier the UaModeler selects the next NodeId, that is not used so far. By default these starting NodeIds are:

NodeClass	Starting NodeId
ObjectTypes	1001
VariableTypes	2001
Objects	5001
Variables	6001
Methods	7001
DataTypes	3001
ReferenceTypes	4001
Views	8001

You can modify these stating NodeIds by selecting the menu entry Settings → Select NodeIds for new nodes.