SUM doesn't add correctly
Using numbers to keep a running total but it doesn't. I have a column of + and - numbers. I entered SUM(B) in a cell. It returns -2071.75. I know that's not right and add with the calculator and get +1458.84. I repeated and got the same. Thus my cell with the formula is showing an error of -3530.59. There is no number close to 3530.59 in the column. This was in a cell at the bottom of the column and I add rows between it and the last entry when I have more to enter. It had worked fine for several years until I installed El Capitan. I have started a new document from scratch and copied the data into it and the same happens. I have entered the SUM formula into another cell in another column and it happens. I have entered the formula both by hand and by the formula box in the toolbar. My sheet has 42 entries, 5 blank rows, and the last row with the sum formula in the cell. There are 6 column but only the one is summed. (or is supposed to be summed.)
What can I be doing wrong? Numbers is version 3.6.1
Geoff
iMac, OS X El Capitan (10.11)