Options Trading - underlying index value difference

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Options Trading - underlying index value difference

Hello, 
Apologies in advance if this query is already answered somewhere, but i cant find it in this forum, hence asking again. 
I'm new to the IG platform and trying to understand the various markets and their prices in this Platform. 
As i browse the options chain for FTSE100 on Nov 24, i notice that the underlying FTSE100 index value is different in options chain with varied maturity. 

for example, at 10:54 AM 
Daily 24 Nov FTSE100 index value -  7482.3
Weekly 25 Nov FTSE100 index value -  7485.3
Monthly 16 Dec  FTSE100 index value -  7497.3

if the underlying index is same, how come the index values is different for each market at any given point of time? 

Please suggest.

Thanks for your help.