Where should I set totalProperty?
http://docs.sencha.com/ext-js/4-1/#!...-totalProperty

You have to set totalProperty in reader, so you can change it in DynamicReader class.

Code:
proxy: {
	reader: Ext.create('Ext.ux.data.reader.DynamicReader', {
		 totalProperty: 'yourValue'
	}),
	type: 'rest',
	url: me.url
}

or


proxy: {
	reader: {
	      type: 'dynamicReader',
	      totalProperty: 'yourValue'
	},
	type: 'rest',
	url: me.url
}
I didn't test this code but should works.