expint function with two arguments

Hello, I would like to evaluate the integral in the picture for t_1=6, t_2=190, delta=0.0011, and kappa=2.1536. Since t_1<t_2, I expect the value of this integral to be positive. However, by using the following code, I get a negative value. In the code, I use the inbuilt expint function of Matlab. Since the denominator's power is 2, I first create a symbolic expression, expint(sym(2), sym(t)), following Matlab's tutorial (https://www.mathworks.com/help/symbolic/expint.html). I would appreciate very much if someone can help me find what is wrong with my code!

        a=sym(2);
        b0=[0.0011; 2.1536]; % b0=[delta; kappa]
        bb0=sym(b0);
        tt1=sym(6);
        tt2=sym(190);
        a1=expint(a,bb0(1)*tt1)-expint(a,(1+bb0(2))*tt1*bb0(1));
        a2=expint(a,bb0(1)*tt2)-expint(a,(1+bb0(2))*tt2*bb0(1));
        x=sym(a1-a2);
        y=vpa(x)

I would appreciate any feedback! I find it particularly difficult since I cannot see how the inbuilt expint function is working....