I agree with what others are saying. One day different in measurements, will not give accurate idea of what is happening.
Two of my horrible experiences with early scans:
I have had two scans (confirming miscarriage) within half an hour of each other with two different machines, and two different operators. One said that I had not yet lost the lining of the uterus, it was measuring over 10mm. The other said the miscarriage was complete and the uterus was normal size!
I had a scan at 7+3 and was certain of my dates and ovulating early not late, measured as less than 5 weeks, no fetal pole. Told to return in 11 days. Where there was a normal pregnancy exactly to dates. By 12 weeks the pregnancy was measuring even further ahead, exactly to my early ovulation dating. So that first scan measured more than 3 weeks out, but produced a totally normal beautiful daughter.
The measurements in early scans are +/- 5 days even with the best equipment and most experienced sonographers. Even at 12 weeks the "accurate time" for dating a pregnancy, is +/- 3days. It is irresponsible of a sonographer to firstly do scans so close together once the pregnancy is confirmed at inter-uterine, and secondly to not be more careful over how the warning that the pregnancy might or might not be ok because of the measurements she has taken vary over 1 days difference. I have had 13 first trimester miscarriages, and I do know how stressful early scans can be. I know that you probably won't take my advice (I know I wouldn't in your situation!), but I would suggest requesting moving the next scan forward to the end of next week, so you get a more accurate picture, rather than test-retest variability.
Please please, try to take one day at a time, "today you are pregnant".