Amount, Cardholder Billing
What it is
Amount in the cardholder billing currency (DE 51) after currency conversion at the rate in DE 10.
DE 6 on the wire
Bitmap position
DE 6 is bit 6 of the primary bitmap: byte 1, mask 0x04. A primary bitmap with only DE 6 present reads 0400000000000000 in hex.
Length
DE 6 is fixed length: always 12 digits, with no length prefix. A parser reads exactly that many and moves on, so shorter values are right-aligned and padded with leading zeros.
Size in the message
At most 12 bytes when the message travels as text (ASCII or EBCDIC), or 6 bytes in binary dialects that pack digits as BCD.
Format n
Format n means numeric: the digits 0–9 only.
Specification reference
Defined in ISO 8583:1987 (base). Card networks publish their own dialect tables (Visa BASE I / V.I.P., Mastercard CIS) that refine formats, lengths, and — for private-use elements — the entire layout. Always confirm against the interface specification you implement.