The following snippet shows how to add the [gamipress_buddypress_group_points] custom shortcode to show the sum of points of group members of a desired points types.

Shortcode attributes:

• points_type: Required. Desired points type to show, Accepts any points type slug
• group_id: Optional. Specific group ID to show the points sum, if not provided, will try to user the ID of the current group

Examples:
Show the group points of Credits:
[gamipress_buddypress_group_points points_type="credits"]
Show the group points of Gems of the group with ID 1:
[gamipress_buddypress_group_points points_type="gems" group_id="1"]

Snippet:

function my_prefix_gamipress_buddypress_group_points_shortcode( $atts ) {

    $atts = shortcode_atts( array(
        'points_type' => '',
        'group_id' => '',
    ), $atts, 'gamipress_buddypress_group_points' );

    $points_type = $atts['points_type'];
    $group_id = $atts['group_id'];
    $points = 0;

    // Bail if not is a valid points type
    if( ! in_array( $points_type, gamipress_get_points_types_slugs() ) ) {
        return $points;
    }

    // If group not provided, use the current group instead
    if( $group_id === '' ) {
        $group_id = bp_get_current_group_id();
    }

    $group_id = absint( $group_id );

    // Bail if group ID not received or can not find the current group ID
    if( $group_id === 0 ) {
        return $points;
    }

    // Get the group members
    $members = groups_get_group_members( array(
        'group_id' => $group_id,
        'page' => 1,
        'per_page' => 999,
        'exclude_admins_mods' => false
    ) );

    if( $members && isset( $members['members'] ) && ! empty( $members['members'] ) ) {

        // Loop members to get each member balance
        foreach( $members['members'] as $member ) {
            $points += gamipress_get_user_points( $member->ID, $points_type );
        }

    }

    // Return the group points
    return $points;

}
add_shortcode( 'gamipress_buddypress_group_points', 'my_prefix_gamipress_buddypress_group_points_shortcode' );