@echo off
setlocal enabledelayedexpansion
set f=x.json
(for /f "tokens=* delims=:" %%i in (%f%) do (
set s=%%i
if "!s:~1,8!" equ "buildver" (
for /f "tokens=1* delims=:" %%j in ('echo !s!') do (
set /a n=%%k
set /a n+=1
echo %%j:"!n!")
)
if "!s:~1,8!" neq "buildver" echo !s!))>temp.txt
move /y temp.txt %f%