What's in a number? When you are meeting someone on a Tinder date, it doesn't matter if there a few years between you - if you hit it off, then that swipe right will have been worth it.
It might be fine in the dating game, but numbers are more clearly defined in rugby. Depending on what digit adorns the back of your shirt, you'll have to perform a different role. Nowhere is this more important than with the number seven.
A lot is made of having a 'classic number 7' in your team if you want to be at the very top. Synonyms of 'classic number 7' include David Pocock and Richie McCaw.
For years George Hook lambasted Irish management for picking Sean O'Brien and David Wallace over supposed breakdown specialists. For some reason being an exceptional ball carrier appears to inhibit your ability to poach... or at least it does according to some pundits.
England's backrow at the World Cup was the perfect example of what can go wrong without an out-and-out seven. Stuart Lancaster opted for Chris Robshaw and Tom Wood in the backrow - two 6.5's as many in the media pointed out.
England went on to lose the turnover battle 8-6 in defeats to both Wales and Australia, results that ultimately doomed their campaign. Pocock's ownership of the breakdown was particularly stark and caused a backlash against the backrow imbalance that Lancaster had cultivated.
In Eddie Jones' press conference announcing his first squad he was very clear about how he was going to construct his back row. Jones cracked a joke about Robshaw's new role in the side and what it would mean going forward.
"Robshaw has been playing really well at 6, probably because he has half a number off his back.
"We aren't going to have any 6 1/2s. We're going to have a 6 and a 7."
That seemed to be the perfect antidote to England's World Cup woes. It was only a question of who Jones would opt for. Would he be able to persuade the RFU to bring the exiled Steffon Armitage home? No, he would not.
What about poachers Matt Kvesic or young openside Jack Clifford? The latter will have to settle for a place on the bench because Jones has chosen to start his first Six Nations game against Scotland with James Haskell at number seven.
Wait, what? Haskell is almost the typical 6.5 - a big, powerful ball carrier and a good rucker, but not the breakdown force of a top-class openside.
By contrast, Scotland - like Wales against Ireland - have picked TWO sevens in John Hardie and John Barclay, which should give them an edge in the turnover battle.
Jones talked a big game but besides reneging on his promise to start a number six and a number seven, he has picked an almost identical side to Lancaster's last Six Nations selection - shelving sensational Saracens second row Maro Itoje for the moment.
If Scotland beat England for the first time since 2008 today, Jones, like Lancaster before him, might have to brush up on his fractions to answer questions on what's the difference between a 6, a 6.5 and a 7.