Thanks all for your replies. So I’ve just done some quick experimentation and got some weird results.
I just played in my head the song and used a different tap tempo on my desktop and got 130. So close enough given I’m just using the beat I hear when remembering the song.
I thought hmmm maybe it’s the justin website tap tempo. Used it on the desktop and again get around 130.
So I use my mobile (which is what I used originally before asking my question) and again I only get 70.
Again thanks all for the help I’ll work on getting my strumming up to 150
