It depends on where you ordered the exmestane from as each research chemical company has a different dosage per mL.
If you ordered it from ag-guys.com or sarms1.com, both of their exemestane is dosed at 15mg/mL. A good dosage for 200mg of test cyp per week is 5mg/mL. This would correlated to a dosage of 0.33mL.