Your first bag of coffee on a new In My Mug subscription will be roasted and posted the next Friday after you sign up :)
In My Mug gets roasted once a week, every Friday. The first instalment of your subscription has it's payment taken when you place the initial order, so that first coffee gets scheduled to be included in our next In My Mug roast on the following Friday. We process subscriptions at 0800 on Friday morning so if your order is placed on a Friday after this cutoff it will get carried over to the following week.
The "next shipment" date that you can see on your account corresponds to the date that the next instalment will be charged - ie it is the next "upcoming" instalment rather than the "present" one being processed.
The way the subscription system works is that it raises an order on the online shop to charge you for each bag, the initial order looks a little messy because it has to be held until the next Friday when In My Mug is roasted and posted, but future instalments will automatically get raised on Thursday mornings ready to be roasted on Friday morning so it's a little bit easier to track :)