Heya, so I've decided to practice some Iron Maiden, and The evil that men do will be my first song but I got a lil problem, what does the "smaller" numbers mean before the normal size numbers, fo' example

small = (x)

G 12 (14) 16
D (12) 14 14

Hope you get what I mean, just need to know how to play it, thanks
where is the tab comming from? a book, online tab, other?
Quote by Dirk Gently
Some pieces are only meant to be played by people with six fingers on their fretting hand. Sorry.
They're 'ghost' notes. Basically this either means they're not played live or they're really hard to hear so only play them if they sound right to you, and if you do play them you should do so gently or subtly.
I think they're the guitar equivalent of the acciaccatura they're notes played quickly as "lead-ins" to the main note and don't take up any beats of the bar themselves.

If you can click with middle finger and thumb then I can give you a good example. Put your index finger right next to your middle finger and click your thumb past both - you've pretty much got an acciaccatura there.
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In this case, for the very first bar you'd play the 12 and immediately play the 14 afterwards - This tends to be accomplished by sliding or legato as the note is a grace note and picking it tends to take up enough time for it to be a recognisable note in the bar.