Zero check and Zero correct of 6514

Hello All,
I don't quite understand the function of Zero check and Zero correct.
What should we do before and after reading a value? that means when to enable and disable the function.
Could you help to explain more about these two functions?  thanks.
 

Hello,
Zero check is a feature that notes the internal voltage offset within the unit. Zero correct allows you to algebraically subtract the internal voltage offset value from your measurement thereby correcting the value of zero within the instrument. Very similar to a REL function, however REL can be used to subtract out ANY level of signal or reading. Zero check/correct is specifically for correcting the value of zero by subtracting internal voltage offsets that would otherwise result in the instrument reading slightly higher than "true" zero.
Zero Check and Zero correct should both be done prior to making a measurement. Zero check willl be disabled to perform a reading.
See the manual I'm attaching below for more info. Ref pages 2-13 and on.
Model 6514 System Electrometer Instruction Manual | Tektronix

Thanks Ty,
Now I'm understand the function of Zero check. But I'm still not sure about the difference between Zero correct and Zero check, It seems Zero check is enough.
How does Zero correct perform on the reading?
Is that means Zero correct is to eliminate the temperature effect?

Zero correction cancels the voltage offset term of the amplifier. With both zero check 
and zero correct enabled, the instrument may not display a perfectly zeroed reading.  
If Model 6514 is operating at, or near TCAL, zero correction will have very little affect. 
TCAL is the internal temperature of Model 6514 when it was last calibrated. 

And on the setting screen of Kickstart which below NPLC, is it Zero check or Zero correct? 
-----------updated: it seems to be auto zero.SYST:AZER

It seems RS232 connection will result in communication error when trying to read the data according to  Kickstart, but setting seems working.

"It seems RS232 connection will result in communication error when trying to read the data according to  Kickstart, but setting seems working"
--> RS-232 has never been supported. GPIB is the proper communication pathway to use with KickStart for this instrument.