Update Slow Time Club to the latest version first. A recent update stops Insights adding in time from other people in your Family Sharing group. Find Slow Time Club in the App Store and tap Update if you see it.
If the numbers still look high
Check Apple's own figure: Settings → Screen Time → See All App & Website Activity. If it's high there too, the number comes from Apple.
If you have an iPad or Mac on the same Apple Account, try turning off Share Across Devices on every device: Settings → Screen Time → Share Across Devices. This can help your iPhone count only iPhone time.
Give it time. Totals catch up during the day, so the number you see at 3pm may be different by 9pm.
Still seeing apps you don't use, after updating? Contact us with your User ID and we'll look into it.
If blocking is acting up as well, see Blocking isn't working: start here.
Why this happens
Every screen-time number in Slow Time Club comes from Apple, and Apple's count isn't always exact. iPhone can include time from family members or your other devices. It can count a website and Safari separately, or count some time twice when you switch apps quickly. We filter out other people's time as best we can, but we can't correct Apple's own counting. Sorry for the confusion.
Still stuck? Contact us from Profile → Help and Legal → Contact support and include your User ID (Help and Legal → User ID).