No big deal if the used space on the 900mb drive is less than the SSD.
Just shrink the 900mb drive active partition to size that will fit the SSD then do the cloning. I do it all the time. Even if the used space is bigger than the SSD, you can off load just the data on the 900mb till the used space is compatible with SSD space, then shrink the partition then do the cloning. I do it all the time. True Image should handle this automatically for you in the sense that it is able to disregard unused space when creating a transferred image so that you dont have to do partition shrinking. You just have to make sure that the used portion of the source is slightly less than the target. I do it all the time.