|In Excel remove the formatting.|
In word, click on your field containing the number.
Press Shift + F9 to display the Mergefield info.
Should look like this:
Right after the name of your field add \#0.0x (0.0x is two decimal places, 0.00x is Three decimals, and so on.)
It should now look like this.
Shift + F9
Try you merge now.