Dynamic Block Creation (Parameter Value Set)

1. Pick Linear Parameter:

In block editor, pick the linear parameter, then click entry frame which is in the right side of "distance type" on Properties panel, there comes one drop-down 

menu.

Therein, none is default option, means can stretch optionally. By other two options, you can define maximum and minimum number respectively. "Increment" means stretch increasingly. If you choose "list", you can set the value , dynamic block can only be stretched accord with the number in the list.

2. Click Text Frame:

3. Test Dynamic Block: