I am playing with the idea of trading some small butterflies in the IWM as opposed to the RUT. I cant seem to get the greeks to fall in line using TOS with the volatility smile setting, comparing a one lot RUT butterfly to a 10 lot IWM butterfly. I realise this is not an exact apples to apples comparison, but to illustrate, I spot checked a 1x RUT Butterfly to a 10x IWM butterfly and these were the results. RUT 1190/1140/1090 for Feb gives me a delta of 8.6 and theta of 9.8. Compare this to an IWM 10 lot butterfly for Feb, 119/114/109 and I get a delta of 68, and a theta of 10.3. The delta/ theta ratios are not even close in this comparison. What am I missing here?