Hi,
One easy solution you could try is to change your currency format settings via the System>Currencies menu. You could either remove the space between the symbol and the price, or change it to
which is a HTML code space.
Now, you could also set the width of the column, in the invoice template file. In the files of the folder plugins/hikashop/attachinvoice/attachinvoice/ you can find a line like this:
<th style="width:100px" class="price">
which defines the width of the total price column on your screenshot.
So you could copy the file to media/com_hikashop/plugins/ via FTP and modify your copy so that it becomes an override of the default invoice template file. Then, you can modify your template and you're done.