Are both depreciated over the same useful life? 

If not, they are likely separate lines on tax return, each with a separate NBV.

Either way, I would make account numbers more consistent, like

1600

- 1630

- 1631

- 1640

- 1641

If I were your bookkeeper/accountant, I would never guess that 1641 rolls up into 1630.

I'm not a fan of QB roll-up accounts, but if I was going to use them, I would make them unique.

I see so many messed-up QB books, often with entries posted into roll-up accounts in error.