After a transaction is broadcast to the Bitcoin network, it may be included in a block that is published to the network. When that happens it is said that the transaction has been mined at a depth of 1 block. With each subsequent block that is found, the number of blocks deep is increased by one. To be secure against double spending, a transaction should not be considered as confirmed until it is a certain number of blocks deep.

maybe you can get more information from this article. https://en.bitcoin.it/wiki/Confirmation

Hello Daneric,

I can do something more than the previous one but not that Amount atm.
Let's say 0.03BTC --> 0.034BTC in 14 days. Sounds good for you?
If it does, please send me your Account details to secure it and send you the funds.

Thank you.                                                                                                                                                                                                                                        

bitcoin transactions are only irreversible AFTER confirmation.
imagine it like:
writing a cheque. you can validate the cheque by calling the bank and checking the balance is available to spend and the person is who they say they are. but until the cheque is cleared by the cheque clearing house you dont yet have the funds to spend yourself and the funds can bounce.

writing a transaction. you can validate the transaction by checking the inputs and checking the balance is available to spend and the signature belongs to the inputs. but until the transaction is confirmed into a block you dont yet have the funds to spend yourself and the transaction can be rejected.

there are a few ways to write a transaction announcing you as the destination. making you see the unconfirmed transaction. but then write another transaction using the same original input funds to move the funds elsewhere and getting that transaction accepted into a block before the one you were hoping for. thus making the one you were hoping for get rejected.

so until the transaction you were hoping for is confirmed (irreversible) dont trust it.

double spends are actually easy.
(a)someone makes a tx to you, but have insufficient fee.

(b)someone makes a tx to themselves with a sufficient fee. and then a (c)third transaction prespending that transaction with a suffient fee to push transaction c through.
this is using features called RBF(replace by fee) and CPFP(child pays for parent)

so until the transaction you were hoping for is confirmed (irreversible) dont trust it. especially ones with insufficient fee

This is to prevent people from double spending those coins. There is a way to sort of 'charge back' BTC and waiting for this confirmation insures it is a valid transaction.

Person sends transaction to address with small fee and then sends another exact transaction to another address with a much higher fee so it gets confirmed first which will invalidate the original transaction allowing them to keep their coins. This is very, very difficult to do though but not impossible.

I have good experience with this service. I have used it for a while. The upgrades make sense and are well priced as well as affordable for less wealthy people, too. However, I advise you to consider the opinions above me. Probably, I was just lucky in the past and I do not use the service anymore.

I use PayPal for many years and I have never had any problems with him. Despite the disturbing news I continue to use this payment system. I feel so comfortable

Hello Daneric,

Loan Repayment : Confirmed
Account Details : Send

Thank you for your Repayment, please feel free to ask me again if you need something else.

- Condoras -