Mac Mini - How to verify cached contents with content caching?

I have a Mac Mini with High Sierra, followed the steps to enable caching per Apple's instructions (https://support.apple.com/guide/mac-help/mchl3b6c3720/10.13/mac/10.13). Now I have multiple iPads (14) trying to download the latest iOS 12.1.1. One iPad is able to pull down the latest iOS fine, but the rest is being sluggish. Perhaps it's due to new iOS release so everyone's trying to download it and maybe it's my own bandwidth, but how do I go upon verifying if the Mac Mini itself is actually caching the latest iOS I just pulled down from an iPad or not? Is there a folder or logs I can check? Thanks in advance!