How P/L is calculated
The exact arithmetic behind the monthly totals, how months are grouped and what the comparison figures mean.
The three numbers
Total spend is the sum of the spent field across all records in the period. Total return is the sum of the return field across the same records. Net position is total return minus total spend. A negative net means more went out than came back.
There is no weighting, no adjustment and no estimation anywhere in this calculation. If you add up the rows yourself you will get the same figures, which is the standard any personal finance number should meet.
How months are grouped
Records are grouped by the date on the record, not the date you typed it. Correcting an entry's date therefore moves it into the correct month and both months' totals update. Months are calendar months in your local reckoning, and the month history lists every month for which you have at least one record.
The previous-month comparison
When last month contains at least one record, the summary shows that month's spend, return and net alongside the change in spend against this month. A negative change in spend means you have recorded less spending this month than last. If last month has no records, no comparison is shown rather than comparing against a fabricated zero.
What P/L does not mean
A positive net over one month is a description of what happened, not evidence of a method. It carries no predictive weight and should not be treated as a reason to increase spending. The most useful thing this page usually tells people is the size of their monthly outflow, which is the number that is hardest to estimate from memory.