Alady walk in a store steals a 100 bucks from the register with the owner not knowing. five minutes later she comes in and buys 70 dollars worth of goods with the stolen 100 and he gives her 30$ in change how much is the owner lose

She goes in, swipes 100 bucks and walks out whistling.

she comes back, he already lost 100 bucks, she comes and buys a pair of trousers and some blouses for 70 bucks, she goes to the counter and pays with the $100 bill.  She doesn't have the $100 bill with her anymore, the owner has it.

the owner grabs the bill, gives her credit for $70 and gives her back $30.

the owner gave her credit for $70 in goods and $30 in change, and she walks out whistling with only $30 in cash and $70 in goods.

he's only out 100 bucks, when she took it he was out 100 bucks in cash, when she bought stuff, he was out 70 in goods and 30 in cash, still just 100 bucks.