Hi Melody - without being able to view your books it's difficult to be precise but, in general terms, the vast majority of accounting takes place on what is known as an "accruals" basis, ie items of income and expense are recorded in the books when they happen, not necessarily when they are reflected in the money that comes into and goes out of the bank account.
In simple terms, it means that income is represented by invoices sent out and expenditure by bills received. So, if I start my business and in the first month, raise invoices for £1,000 and receive bills from suppliers of £700, I've made £300 profit, regardless of how much of that money has been paid into, out of, the bank.
In addition to the above confusion, I may well have started my business bank account with £100 of my own money, effectively as a loan, to be repaid when the business is up & running. As a loan, this £100 is not income and so does not add to the profit.
I'm afraid I don't understand what you mean about the rounded up/down numbers, can you be more specific?