The number of deviced used at the same time to connect with a VPN varies per VPN-provider. 3 To 5 devices is very common. This means that this number of devices can log in to the VPN account on the same moment. Number 6 will receive an error when trying to connect.
You should know that ExaloVPN is available from €5 per month with an annual subscription. You can use 5 devices at once with any subscription on ExaloVPN.