how long I have to wait usually?

I found out the transfer because I filed I-601 for vaccine waiver according to:
http://www.uscis.gov/portal/site/uscis/menuitem.5af9bb95919f35e66f614176543f6d1a/?vgnextoid=d0943591ec04d010VgnVCM10000048f3d6a1RCRD&vgnextchannel=52a46c854523d010VgnVCM10000048f3d6a1RCRD,

Usually how long it takes to have appointment scheduled? Thanks a lot!