A7000 connects to iPhone 8 Plus hotspot only at 802.11n

My laptop is a Thinkpad E530 with 802.11n WiFi and so I bought A7000 AC1900 adaptor as an upgrade.

This is what I did.

- I installed this software to my Windows 10 laptop. http://www.downloads.netgear.com/files/GDC/A7000/A7000_V1.0.0.15_Windows.zip

- I plugged the A7000 adaptor to the USB 3.0 port of my laptop.

- When I connect my the A7000 WiFi to my iPhone 8 Plus hotspot, it can only connect as a 802.11n standard instead of 802.11ac

- I thought I used the built-in 802.11n WiFi adaptor to connect to my iPhone hotspot and so I disable the built-in WiFi adaptor

- Then I reconnect the remaining WiFi adaptor (i.e. A7000) to my iPhone hotspot but the connection still shows 802.11n.

How to connect to my iPhone 8 Plus with 802.11ac standard?

Please help.