difference between 0PU_IS_PS_41(Budget Totals Records) and 0PU_IS_PS_31(Commitment Line Items)

Hi expert,

      I am working on datasource 0PU_IS_PS_41(Budget Totals Records) and 0PU_IS_PS_31(Commitment Line Items), I think those two datasource should be consistent for data. but I have commitment line item data for 2014/2015/2016/2017/2018 , but in Budget Totals Records, only have data for 2014/2015. so from data point of veiw, what is difference between these two data source?