it dpends on the time signature of the song.
since your asking about 16 bars, i assume its hip-hop?
a bar is 4 counts. (1 and 2 and 3 and 4 and)
tap your foot to the beat. every forth hit of your foot against the floor = 1 bar.
start over after 4. (1 and 2 and 3 and 4 and 1 and 2 and 3 and 4 and...etc...)
Since he dosnt know how to count bars, but knows there are 16 bars in a normal verse, i figured him for a hip-hop head.
"16 bars" is a slang term for a verse in hip-hop.
people always say "I drop hot sixteens", instead of saying they have good lyrics.