What is the difference between stage one and two BC

I was diagnoised with stage 1 Lobular Breast Cancer on Monday.  They definatley said stage 1 and my daughter was with me and heard the same. But recieved a copy of the letter that they sent to the GP this morning and it says stage 2 16mm.  It then says ER8 PR7 Her-2 0 negative Ki67 5%.  I do not know what any of this means can anybody help?

Also was told I would have MRI scan and ultrasound this Wednesday  with results at follow-up appointment with consultant Friday on 26 and surgery 9 October.  I have the letter to go and see the consultant for my results on Friday as plan but recieved another letter this morning saying my MRI and Ultrasound is not until 4 October which is the week after!  I am so fed up of waiting and worrying