I'm guessing your checkboxes end up something like
1  1
---
2 2
---
3  3
---
4 4
(dashes denote frame separation)

If you want them to be aligned with any amount of text, you should use two frames as follows:

1 | 1
2 | 2
3 | 3
4 | 4

This is using two frames each packed to the left.
One frame contains the first check box for sets 1-4, the
other contains the second check box for sets 1-4.