They are calculated by substracting the estimate of incremental tax collections from disallowing deductibility given in column(2) from the corresponding estimates of gains from assumed tax cut given in column(3).
这个句子我知道它的意思是列（3）-（2），可是中间的一堆东西，看不懂是什么意思，求好心人帮下忙，谢谢！