Join ultimate for £1 offer? Xbox gold to game pass ultimate.

Have I got this right that the 'Join ultimate for £1' offer on the xbox dashboard converts all my current remaining xbox gold subscription to game pass ultimate for just £1 one off fee?

Text says: 'Joining xbox game pass ultimate will upgrade your remaining xbox live gold into Game pass ultimate for the same amount of time, up to 36 months. All conversions final'

Currently I have over 2 years gold subscription built up and it seems a bit to good to be true to convert all that for just £1.

Have I got it wrong and it's £1 a month or just £1 for the first month? I keep finding conflicting information. If so the 'all conversions final' bit worries me a little.

Thanks for the help

:)