In Turbocash my C= bit at the bottom of the screen keeps showing minus am I doing something wrong?

I've just started converting my accounts from spreadsheet to Turbocash.

At the moment I'm putting the invoices in to the system and then going into the Link menu, finding the invoice and marking it as paid when it's been paid

When I go into the ledger report all the payments show up as sales and they go into "CURRENT ACCOUNT" journal but at the bottom of the report it always says something like

C=-1600

D=0

I'm guessing the D is debits (expenses) and the C is credits (income) but is there a reason C is showing a minus value? Am I doing something wrong? Do I need to link the transactions up somehow from the current account journal or is this just normally how accounts work with credits shown as a minus number?