以下用英文講應該點講

in england, we would say:

1) please sign anywhere on the receipt.

2) four hundred dollars change.

1. Please sign on any spaces of the invoice.
2. Here is your change of $400.

1) Please take a post in the invoice what position signature
2) Find back$400

1) Please sign on the invoice. (I suggest that there is no need to mention 任何位置)
2) $400 change