Brother FAX-1820C - Manual (Page 127)

MAKING COPIES 10 - 11
4 in 1 (P)
If 2 in 1 or 4 in 1 copies are in color, you must use letter or A4
paper. For the other Special Copies, you must use letter, legal
or A4 paper.
If you selected Glossy in the Paper Type setting, 2 in 1 and
4 in 1 copies are not available.
2 in 1 or 4 in 1 copies in color are not available with Multiple
Copies.
(P)
(L)
4 in 1 (L)