more md fixes

content/pages/15percent.en.md

@@ -16,6 +16,12 @@ The 15% applies to the day rate of Varia on work commissioned to one or more Var
 
 # How is it calculated?
 
+Varia is a registered non-profit association that charges BTW. 
+
+The 15% is calculated before BTW/VAT has been added to the final fee.
+
+Here is an example of how it is calculated, using Varia's day rate:
+
 > Varia works with a day rate of **250 EUR**.
 > On top of that, we calculate the 15%, which is in this case **37.50 EUR**.
 > In total, this is a day rate of **287.50 EUR**.