examples: csv: note issues with b of i balance assertions

examples/csv/bankofireland-checking.csv.rules

@@ -11,6 +11,12 @@ skip
 
 # name the csv fields, and assign some of them as journal entry fields
 fields  date, description, amount-out, amount-in, balance
+# Note: we generate balance assertions from the balance field here,
+# but you may sometimes need to remove these because:
+# - the CSV balance differs from the true balance, 
+#   by up to 0.0000000000005 in my experience
+# - it is sometimes calculated based on non-chronological ordering,
+#   eg when multiple transactions clear on the same day
 
 # date is in UK/Ireland format
 date-format  %d/%m/%Y