Forwarding just one port

Hi,

How do you forward just one port?

In WAN -> Port Forwarding, options are:

Port Range
Local Port

'Port Range' won't accept just one port (e.g. 44221) and it won't accept the range 44221:44221. It needs a true range like 44221:44222.

Setting just 44221 in 'Local Port' gives an error requesting 'Port Range' to be set up.

So, how do you actually forward just one port?

Thanks