You would just add an extra <br /> where you want an extra line.
HTML Code:
<br /><span class="shade">{vb:rawphrase x_members_and_y_guests, {vb:raw content.numberregistered}, {vb:raw content.numberguest}}</span><br /></p>
<p>{vb:rawphrase most_users_ever_online_was_x_y_at_z, {vb:raw content.recordusers}, {vb:raw content.recorddate}, {vb:raw content.recordtime}}<br /></p>