Metronomes

8-yr-old boy is really unenthusiastic about violin (his dad makes him have lessons).  Last week, I said he needed to get acquainted with a metronome - best thing ever.  He loves it, I think because he gets to use his dad's phone, and he uses it every time he practices.  We put it on today, for a Minuet by Bach which has ta = 100-115 at the top.

Boy: I don't know what the hundred means.
Me: See how there's a ta there?  So you put your metronome onto to 100, and that's the same as your ta beat.
Boy: Oh.  [plays a bit] But that's so fast!
Me: Well, as you've only had this piece a week, we could make it a little bit slower.  Let's try 90. [Boy adjusts metronome, and we play a few phrases at that speed.  The opening passage is a bit of a challenge though].
Boy: Oh but it's so fast.  This piece is so hard!
Me: You know, we could put the metronome on even a bit slower.  Your examiner won't have their own metronome on, saying "Ahem, it's meant to be 100 and you're only playing it at 99".  If it was on.. 60... Then they might say it's a bit slow.
[Boy changes tempo to 81.  We play a bit more].
Boy [grinning cheekily]: Good thing we didn't make it 80.  They'd probably say something then.