Data for the stock value report is available from February 2023. This is a new report and won't show historic data prior to this date.
The stock value report summarises the value of stock per supplier and all your stores. You can use this report to:
Discover which suppliers you hold the most stock with
Provide your accountant with stock value figures over the past 12 months
By default, the stock value report shows the total value of all stock in the last 30 days. Tap No grouping to group stock by store or supplier. Selecting Group by supplier lists all suppliers individually, with the total stock value associated with each supplier. Selecting Group by store lists the total stock value per store.
Export report
Tap 
then Export to export all data within the filtered report.