Below are definitions for the cost and consumption metrics for GCP FlexReports:
Cost refers to either on-demand cost or credit cost depending on the type of line item.
Total cost always refers to on-demand cost for every line item.Consumption is mapped to usage.amount column from big query.
Consumption_In_Units is mapped to usage.amount_in_pricing_units from big query.
Please refer to the description from below link for more details:
https://cloud.google.com/billing/docs/how-to/export-data-bigquery-tables/standard-usage