cannot remove test booking

collections/_documentation/contract.md

@@ -62,6 +62,10 @@ As you can only lock complete months, it is currently only possible to change th
 
 ## Manual bookings
 
+Attention: perform tests on a separate test account (or the [demo environment]({% link _pages/demo.md %})).
+
+You cannot delete manual bookings, so if you accidentally added wrong values, simply create an opposite booking and add something like "compensation for test booking" in the description.
+
 ### Account working times
 
 Manual bookings can be used to increase or reduce the users time account.