How can I get rid of the extra zeroes showing after the decimal separator?

You can enable the setting the truncate the extra zeroes that are shown after the decimal value.
To do so please follow the below steps :

1. Click on your User icon on the right top of your Vtiger page
2. Click on My Preferences
3. Click on the Edit icon
4. Enable the Checkbox Truncate Trailing Zeroes



Refer : My Preferences