Bulk discount create draft orders for your customers containing the appropriate discounts.
Draft orders in Shopify work a bit differently from regular orders.
To view stats on orders that originated from a draft order, Shopify recommends running a 'Sales by Channel' report. Shopify has details on their support page at:
https://help.shopify.com/manual/reports-and-analytics/shopify-reports/report-types/sales-report#sales-by-channel