How to account for better performance when finding confidence intervals?

Hi,   Please correct me if I'm wrong about this. In the confidence intervals practical example, we find the 95% CIs for each shoe size so that we can stock accordingly and avoid overstocking. However, this is all based on past data. What if I knew Al Bundy was making a strategic plan in order to double their sales in the next year? How do I take this into account so that my confidence intervals reflect a better performance? Should I multiply my data by a factor or something?   I'm sorry if this is explained in another section further ahead.   Thanks.