If you subscribed through Apple In‑App Purchase, Apple often attaches an introductory period (sometimes shown as a free trial — exact wording and length appear on Apple's checkout screen; seven days is typical).
During that period payment usually hasn't cleared yet, so the remaining time you see in the app (for example about seven days left) usually reflects the trial window, not your full monthly or yearly entitlement already granted.
After the trial: if you have not cancelled before it ends, Apple begins the paid subscription, and your membership duration then advances according to the plan you chose. You may cancel anytime during the trial from Settings → Apple ID → Subscriptions (or the subscription section in the App Store) if you don't want it to renew automatically.
Note: Exact billing timing follows Apple's receipt and subscription terms; wording may vary by region.
