You can set product sell/purchase in weight, so you can set this option from product form view

Go to Purchase >> Reports >> Updtae Transactions Records, To insert new reocrds and update existing records.

Go to Purchase >> Reports, in that you can find PO Rate Variance Report. Here you can see all the records that describe variance

Form view of PO Rate Report look like this

Can print report in multiple format PDF and XLS, To print select records and click PO Variance Report from action

Now, Select any format and click on Generate button to generate report.

On clicking Generate button you will see report download option. Download on click download icon

Go to Purchase >> Reports, in that you can find Bill Variance Report. Here you can see all the records that describe variance

Form view of Bill Rate Report look like this

You can generate bill variance report step by step as PO rate report