After creating a btree with 279 entries, wt dump shows 279 entries, and wt stat reports 281 for btree: number of key/value pairs. The difference arises because entries in internal pages that point to subordinate pages are counted in this statistic. The btree for this case looks like this:

       |
  Internal page
   /        \
Leaf       Leaf

We show:

  btree: number of key/value pairs=281
  btree: row-store internal pages=1
  btree: row-store leaf pages=2

To get the "right" answer in a row store with current stat output, one needs to calculate: E - I - L + 1, where:

E  == btree: number of key/value pairs
I  == btree: row-store internal pages
L  == btree: row-store leaf pages

Or are there more factors to consider to get an accurate view? At any rate, this seems confusing and makes it harder to use wt stat as a quick diagnostic tool. It came up as part of SUPPORT-1248.