You cannot change an estimate's number once it has been created. However, follow these steps to change the next estimated number you want to use.

​Step 1: Go to Settings > Estimates

Step 2: Click on "Next Estimate Number"

Step 3: Choose the next number you want to use.

Step 4: Save.
​

Step 1: Go to Settings > Estimates

Step 2: Tap on "Next Estimate Number"

Step 3: Choose the next number you want to use.

Step 4: Save.