How to reduce space between 2 label on a Grid??

I have a Grid with 2 label and I want minimal space between, but I'm not be able to reduce it.

I've tried RowSpacing="1" but it doesn't work

  <ContentPage.Content>

            <Grid Padding="20, 0, 20, 20" >
                <Grid.RowDefinitions>
                    <RowDefinition Height="Auto" />
                    <RowDefinition Height="Auto" />
                    <RowDefinition Height="Auto" />
                    <RowDefinition Height="Auto" />
                    <RowDefinition Height="Auto" />
                    <RowDefinition Height="Auto" />
                    <RowDefinition Height="Auto" />
                </Grid.RowDefinitions>


            <Grid Grid.Row="0">
                <Grid RowSpacing="1"> 
                    <Grid.RowDefinitions>
                        <RowDefinition Height="Auto" />
                        <RowDefinition Height="Auto" />
                    </Grid.RowDefinitions>
                        <Label Text="FisrtLabel" FontSize="60" HorizontalOptions="Center"  Grid.Row="0" TextColor="Black"/>
                        <Label Text="Second" FontSize="16" HorizontalOptions="Center" Grid.Row="1" TextColor="Black"/>
                </Grid>
            </Grid>

....

How could I fix it!?