Update: Before our change the GridViewGroupFooterCell content was right aligned and the GridViewFooterCell content was left aligned. We decided to unify them by setting default left alignment to both. This can be easily modified by changing the Column FooterTextAlignment property to Right or by using the following implicit styles: 

<Style TargetType="telerik:GridViewGroupFooterCell" BasedOn="{StaticResource GridViewGroupFooterCellStyle}">
    <Setter Property="HorizontalContentAlignment" Value="Right"/>
</Style>
<Style TargetType="telerik:GridViewFooterCell" BasedOn="{StaticResource GridViewFooterCellStyle}">
    <Setter Property="TextAlignment" Value="Right"/>
</Style>

The fix is available in R3 2017 of UI for WPF.