Walgreens Clipper Card Purchase and Load Time

Just bought a Clipper Card from Walgreens along with an initial cash value load of $40. I was under the impression that this immediately transferred the value to the card. However, when I got home and registered the card, there was no balance on it. Am I waiting for the once-daily update from Walgreens to Clipper? Or do I just need to tag in at a BART station?