label list S1410
label list S1411
label list S1412
tab1 s1410-s142,m 

Variables s1411 and s1412 only apply to the persons who respond "yes" to s1410.  If "No" or "Don't Know" on s1411, then they are NA for s1411 and s1412 and have a dot (".") code on those variables. Here is the value label for s1411:

. label list S1411
S1411:
           1 in the last 12 months
           2 more than 12 months ago

The variable label is poor.  I assume that the correct variable label for s1411 would be "last time were told you had tb".  It appears to me that all you want to do is to change code 2 to code 0. There are many ways to do this but here is one:

gen s1411r=s1411
replace s1411r=0 if s1411==2

label define S1411R 0 "more than 12 months ago" 1 "in the last 12 months"
label values s1411r S1411R