You want to change an alert threshold in a SAP-delivered monitoring template. Why shouldn't you edit the standard template directly, and what should you do instead?

Don't edit the SAP standard template directly. SAP delivers and updates standard monitoring content, so any change you make to a standard template is overwritten / lost on the next content upgrade.

Instead:

• Copy the standard template into a custom template (SOLMAN_SETUP → Technical Monitoring → Template Maintenance → Create Custom Template).
• Assign the custom template to the managed object and edit the copy.

That's why copying is effectively a must, not just good practice: it's the only way your thresholds and alerts survive SAP content upgrades.