the software too you are using is showing the same SSID twice because there are two devices advertising their existence (beacons) using that SSID.
WiFi and the IEEE 802.11 standards do not require a client device (PC, laptop, device) to choose the strongest signal, or re-choose due to movement of the device.
Therefore, some client devices choose "first-heard" in a scan, and other choose best-signal in a scan. Few or no consumer WiFi clients re-scan to find a "better" signal when the signal strength us usable (but weak/slow speed).
So, there's no ideal seamless with consumer WiFi.
If your devices always choose the best signal, then leave it as is- one SSID.
If some devices sometimes choose the sub-optimal access device ( AP, WiFI router), and that leads to a too-weak signal, too slow speed, then about all you can do is the following. Put the AP on a different SSID. The user then has to "know" which SSID is best in what parts of the house and choose manually.