There are several resources:

- You can adjust the walls position manually moving the walls with the arrow keys or using Edit => Move => type the exact distance.

- You can set the exact dimension selecting the wall using the arrow with the # sign (outlined in green in the image attached) => point a wall with this tool => write the desired length.

- You can draw a wall to the exact length using the "Wall (Custom Length)" tool (outlined in red in the image attached) => select the tool => write the desired length.

- You can remove the unnecessary wall breaks using the "remove point tool" (the dot with the minus sign outlined in blue in the image attached).