R中的时间序列分析:ts()函数中的频率值vs acf图中的滞后

I am a newbie in time series analysis. I am having monthly sales data for 60 months, from January-2009 to December-20013, and trying to forecast sales for upcoming 6 months via ARIMA model. I read the data and convert it into time series object as follow : I am a newbie in time series analysis. I am hav