Try this :
<xctk:IntegerUpDown x:Name="integerUpDown"
Margin="5"
Minimum="0"
Maximum="10">
<xctk:IntegerUpDown.ToolTip>
<ToolTip DataContext="{Binding Path=PlacementTarget, RelativeSource={RelativeSource Self}}">
<StackPanel>
<TextBlock Text="{Binding Minimum, StringFormat=Min: {0}}" />
<TextBlock Text="{Binding Maximum, StringFormat=Max: {0}}" />
</StackPanel>
</ToolTip>
</xctk:IntegerUpDown.ToolTip>
</xctk:IntegerUpDown>