Most shippers claim that they package their stock to survive 2 days in the bag, just in case. But it's an awfully stressful situation so every hour you can knock off is good.
I've had good luck having a neighbor bring the box inside (or in your case receive it at work) so it's not having crazy temp swings. I didn't even open the box until I was home and had everything set up to move them. Then a quick acclimation to get them out of the icky water. Just 15 minutes float to even out temp, open bag, check salinity, match the water to the bag water and get them out. There will be a lot of waste buildup so you don't want them sitting in there once it's open, ammonia will start burning them almost instantly.
The risk is that if anything doesn't make the trip, you may get stuck if you seek a credit. The seller will be able to see that they were delivered at 10:00 am, so if you are emailing them at 7:00pm and trying to say the fish was DOA they might be reluctant to refund.