The period doesn't always mean the same thing
One report may use created date and another the close date or stage change. Make sure you use the same cut-off and time zone, then confirm when Analytics last synced.
If the source doesn't keep enough dates or history, document the limitation instead of rebuilding stages with assumptions.
Relationships and duplicates
When joining deals with line items or activities, a deal row can repeat. Decide whether you count unique records, line items or amounts, and test one-to-many joins.
Quotas and deals need the same level of aggregation: period, user and business line. Exclusion rules must be applied explicitly.
A reproducible validation
Pick a sample and check each value against the CRM, then review aggregations. Write down source, cut-off date, filters, duplicate handling and exclusions for each KPI.
On real projects this is how revenue classification, churn definitions and forecasts were fixed until dashboards matched finance.
To review your situation we need one concrete process, its source data and the expected behavior. Book a free 30-minute review and we'll tell you what to do first.