That's quite easy to do at the drags just from experience and knowledge. In some races you can make 0.75sec on the other driver just in reaction time and 0.25sec in 60ft time, so theirs 1 full second in the first 20m which has absolutely nothing at all to do with engine power. At 1 of my last drags I did I raced a forum member whom had around 250-260rwkw (180rwkw for me). I knew he'd get me easily in the TS so I made an extra effort to get off the line before him and make him run me down. As above I had him easily in the Reaction and 60ft and even by 3/4 track but in the last 100m when his turbo kicked in he blew past me like I was standing still. I did a 14.1sec and he did a low 13sec pass. They are 2 completely different things. A Dyno measures how much power your engine is making minus the drivetrain loss giving a result. It doesn't matter whether it's your mum revving out your engine or the guy from your local fish & chip shop as it is still going to give the same result on that dyno.
A 1/4 Mile drag race measures how good your suspension setup is, traction, accelleration, top end, driver ability, track preperation, weather conditions, experience, knowledge and how big your balls are.
I'd be pretty happy with that. I think 108mph (not knowing what your 60ft was) would be good for a 12.9sec pass though, hell I see torana's doing low 12's with only 108mph every wednesday night so its not the TS but more so the first 330ft is where all the time is made, after that it comes down to just pure horsepower. I wish, i'm at ~180rwkw and can't for the life of me beat a 14.1sec I'm determined to break into the 13's before I sell my car though.