You should be able to carefully apply some acetone to so kind of cloth or brush and very precisely get it onto the thread. It’ll take some time but because it evaporates so quickly I guess you should be able to do it without getting it onto the finish in the process
English has four-teen fif-teen etc. up until twenty and from that point forward has the decade in front of the single number twenty-one. In contrast to German which at least Always has the single digit in front of the decade