If you're referring to the spacing left and right of Σ, it is there so that the summation criteria you've written can be displayed. Perhaps this?

"" <= sum from{binom{[x_{i-1},x_{i}]}{ " " subset K} } %epsilon %DELTA x_i +

sum from{binom{[x_{i-1},x_{i}]}{"="[u_j,v_j]} } 2M %DELTA x_i <= %epsilon (b-a) +

2M sum(v_j - u_j) underbrace{""<%epsilon} <= %epsilon(b-a+2M)

If not, how would you propose to display the summations without this spacing, while showing the criteria?

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Mr. Programmer

AOO 4.1.7 Build 9800 on MacOS 10.14.6. The locale for any menus or Calc formulas in my posts is English (USA).