“cалмак” means “weight “(kilo).“-дөн” means “than the”, that is, “comparison”.
Бул короз жөжөдөн салмагы абдан оор эле=Cock’s weight was much greater than the weight of the chicken. Of course, it's true.
But here, what chicken? Кандай жөжө? -- (өзү менен тең) жөжө. “Тең” means “Equal” (=),
so “короз = жөжө” is not true.Since speaking person has in mind a lot of chickens, it may be 1короз=2 жөжө, but here, we have in mind is very heavy (абдан оор).