@echo off>output.txt & setlocal enabledelayedexpansion
set input=input.txt

rem this finds the text INTERPOLATED HYDROGRAPH in the input file
rem sets k0 = to that line#
rem sets x = to that line# + 6 and
rem sets y = to that line# + 8
for /f "tokens=1,5 delims=[] " %%a in 
   ('find /n "INTERPOLATED HYDROGRAPH"^<%input%') do (
set /a x=%%a+6
set k0=%%b
echo line !x!
set /a y=%%a+8
call :xx
)
goto :eof
:xx

rem this line takes the line #s and extracts the following:
rem 2nd column of line !x! and the 6th columns of line !y!

rem find /n /v ""<%input%|findstr "^\[!x!\]"
for /f "tokens=2 delims= " %%a in 
   ('find /n /v ""^<%input%^|findstr "^\[!x!\] "') do set k=%%a
for /f "tokens=6 delims= " %%a in 
   ('find /n /v ""^<%input%^|findstr "^\[!y!\] "') do set k2=%%a

rem this writes the values to a text file
>>output.txt echo %k0% %k% %k2%