BTW, for future users, if one wanna make the font even smaller or larger then use more tags, for ex:
function OnStart()
{
lay = app.CreateLayout( "linear", "VCenter,FillXY" );
txt = app.CreateText(null, null, null, "Left,Html,Multiline");
var largeFont = '<b><big><big><big>big bold</big></big></big></b>'
var smallFont = '<small><small><small>lower small font row</small></small></small>'
htm = largeFont + '<br>' + smallFont
txt.SetHtml( htm )
lay.AddChild( txt );
app.AddLayout( lay );
}