This is a term in the Philippines’ traditional measurement system.
gá·tang
gatang: chupa (0.37 liter)
– 1/16 of a salop
– estimated to be about 0.3 pounds
spelling variation: gántang
MGA KAHULUGAN SA TAGALOG
gátang: takalán ng bigas at iba pang butil na karaniwang yarì sa láta ng gatas o biyas ng kawayan
gátang: takal na katumbas ng 1/8 ng isang salop
gatángin, gumátang, igátang
Sa mga Bisaya, ang gátang ay takal na katumbas ng tatlong litro.
Sa wikang Sebuwano, ang gátang ay bungkos ng dahon ng tabako.
KAHULUGAN SA TAGALOG
di-mahapayang gatang: mayabang
From my recollection, 1 gatang was about 1/9 of a salop. A seller would use a can of condensed milk (about 330 ml or .33 liter, which is rather close to the 0.37 liter given here) to measure a gatang. As defined in this dictionary, 1 salop is 3 liters, which would make 1 salop roughly 8.11 to 9.1 gatangs, depending on whether you are using .37 li or .33 li, respectively.