Brother FAX-1820C User Manual page 124

4 in 1 (P)
(P)
4 in 1 (L)
(L)
If 2 in 1 or 4 in 1 copies are in colour, you must use 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 colour are not available with Multiple
Copies.
10 - 15 MAKING COPIES