How am I listening to a disc with 150 mins of Audio on a SP MZ-R70???

[NEOband]

Forgive my ignorance on this but i'm alittle confused as a newbie.

 

I found a disk that has 150 mins of music on it, about 30 tracks. The music plays fine and I can skip through all tracks. The player is a Sony MZ-R70 which is a SP player only. Its not LP2 or LP4. I thought a unit had to be LP2 or LP4 compatible to play a disk that was created on a LP2 or LP4 unit.  Google says the unit will play whatever the disc contains but somethings not right. However I do have some discs that will not work on this unit as they where infact made with LP2 audio. So how on earth does this disc have 150 mins of audio on it and work in the MZ-R70???  When i select to show All remaining recording time availble it says 74 mins.  How can this be as it has 150 mins of audio on it. Its cool, but weird 🙂

 

Can someone clear up my confusion please.

Much appreciated.

[BearBoy]

Hello. Is it possible the recordings are in mono? Mono SP would give you 160 minutes on an 80 minute MiniDisc.