This question comes up from time-to-time on the FrameMaker lists, so I will illustrate the problem and solution with four screenshots. You have a single table anchored in a paragraph in the left column. As the table flows from column-to-column, the top of the table in the first column does not line up with the top of the table in the rest of the columns.
To remedy this, you need to change settings in two dialog boxes. First, click in the anchor paragraph and bring up the Paragraph Designer. Change the Line Spacing to 0 points and the Space below to -2 points and click Update All. Go to the Default Font area of the Paragraph Designer, set the Font Size to 2 points, and click Update All (not shown in the screenshot). You won’t see a change until you do the next step.
Click in the table and open the Table Designer. Change the Space Above to -2 points and click Update All.
The table tops in all of the columns will now line up with each other.