This is a number representing 1,200,000 (one million two hundred thousand). In Chinese, large numbers are grouped by ten-thousands (万), so 1,200,000 is expressed as 一百二十万 (one hundred twenty ten-thousands) in standard speech. The form 一千二百万 (literally 'one thousand two hundred ten-thousands') is a colloquial variant, common in informal contexts like talking about prices or populations. The POS 'm' (measure word / numeral) means it functions as a number that can be followed by a classifier when counting objects.