If someone, stole $100 from the cash register, and spent $70 and gets $30 in change how much did the person that owns the store lose

It's $170

Assuming the person stole the money from that store that they do the transactions. And the person who stole the money is broke.

Initially $100 is stollen

Total: - $100

Then the person uses $70 to buy goods. Since the goods are bought with stolen money, these are stolen goods and now their value has to be added.

Total: - $170

Then the guy gets $30 in change. This is an equal exchange process so no money is gained nor loss.

So, the store has loss $170 total.

you didn't specify if they purchasing from the same shop, as they stole from, so it's just an assumption at this stage, you might want to word the question better.

Roughly $100, that's assuming the item that was bought for 70 was worth 70.

They took a hundred, traded it back for $30 cash and an item that is presumed to be worth $70, 70+ 30= 100.

I said $70 then I said $30