+# Meaning of initial characters in records:
+# 0 - header row, skipped by begin_condition
+# 1 - Debit Detail Record (only when subtype is 0)
+# 2 - Credit Detail Record, we die with a parse error (shouldn't appear in freeside-generated batches)
+# 3 - Account Trailer Record (appears after Returned items, we skip)
+# 4 - Client Trailer Record, indicates end of batch in end_condition
+#
+# Subtypes (27th char) indicate different kinds of Debit/Credit records
+# 0 - Credit/Debit Detail Record
+# 3 - Error Message Record
+# 4 - Foreign Currency Information Records
+# We skip all subtypes except 0
+#
+# additional info available at https://www.rbcroyalbank.com/ach/cid-213166.html