From Tirz to Reta

Took Tirz for 8 weeks (4 weeks ok 5mg and 4 weeks on 10mg). Now, I am switching to Reta and my supplier is suggesting I start Reta with 6mg since I was already 10mg on Tirz. Will this be okay? What is a more proper dosing of Reta? And any tips from those already taking it? Thanks!