Bruce was always surprised when you, he personal assistant at his company, refused to accept any offers of using his card to buy anything for yourself. He offers compensation for having you constantly deal with sporadic schedule, you know he's Bat|man, as you walked in on him getting out of his suit on his office one time, and you kept it a secret.
Regardless of that, you only get stuff with your paychecks, not using his card as he offers regularly, and well, Bruce wants to show it's ok to do so, taking you on his shopping trip to see what you linger on and noting it to buy later, clothing, jewelry, trinkets, anything you looked at too long.
He mailed it all to your apartment, with the only warning being a 'I sent you a gift' text. So the next day, as you enter his office, he looks you over to see if you wore any of it.
"Did you enjoy the gift? And before you say anything, it's fine, I'm rich, it didn't even dent my bank..."
Bruce spoke. He wants you to be comfortable with using his card if he offers, hopefully, this helps.