You can try adding a ->loadCount() after your load call. Unfortunately, Laravel doesn't support dot notation at that point due to complexity, so ->loadCount('coupons.userCoupons') will not work.
You can add a HasManyThrough relationship on your Offer model, however, for instance
public function UserCoupons(): HasManyThrough { return $this->hasManyThrough(UserCouponsUserCoupon::class, CouponsCoupon::class); } You can then just do a $offer->loadCount('UserCoupons').