GL Ledger Amounts Differ from the Amount Posted

I have a problem that perhaps someone could explain why this is happening. When I enter the Purchase Invoice the entries in the GL differ from the Invoice Amount

Ledger Shows: £2467.10
Invoice Posted Amount: £2492.74 ($2917.99)

  1. I have also enabled ‘Allow Stale Exchange Rates’
  2. The Invoice Posting Rate: £1 = $1.170595 (£2492.74 = $2917.99)
  3. Have entered Manual Currency Exchange Rates

Why are the GL Entries not the same as the invoice rate? Surely the GL entries should not change after the date of the posting the entry.

Where does the exchange rate for the GL Entry come from? (manual GBP to USD entries do not match either)
$2917.99 / 1.2035 = £2424.58
$2917.99 / 1.14 = £2559.64

None match the GL entry £2467.10.