468060 (64) [Avatar] Offline
.enter() 'fires' once and returns an object which contains eight placeholders. It doesn't 'fire eight times'.

Nor does it 'define how to respond when there's more data than DOM elements'. (p.64).
elijah.meeks (123) [Avatar] Offline
The enter behavior is literally the behavior when more data is bound than elements in a selection. It's quite clear to folks what that language signifies, but I'll tighten it up in case anyone who reads this is overly pedantic in the way that they approach programming and that throws them off.
468060 (64) [Avatar] Offline
My worry is that 'firing eight times' suggests that the function is being invoked eight times in some kind of loop.