Upgrade Plan & Billing

Hi I have Ring Protect Basic Plans for my spotlight cam and my doorbell cam. I want to add my indoor cam to it too and have the Protect Plus plan. The problem is that only 5 days ago I was charged my monthly fees for my exisiting plans, and I don't want to subscribe to the Plus plan right now if it will charge me straight away. Will I get charged a pro rata or can someone provide any info? I'll attach a screenshot to show what it says. Cheers.