why the time "t" inside the ode solver OutputFcn is not a scalar?

For an ODE problem that I have, I need to evaluate some values right after each successful ODE step. therefore I decided to use OutputFcn (output function that is supposed to run only successful steps). I wrote a code and here is its summay:

options =odeset('OutputFcn',@My_OutputFcn,));

[T,Y]=ode15s(@ode_func,[simulation_time_start,simulation_time_end],initial_conditions,options]

%%%%%%%%%%%%%%%%%

where the OutputFcn is:

function status = My_OutputFcn(t,y,flag,varargin)

global force
t
force= force+t;

%%%%%%%%%%%%%

but the problem is that in the above method, sometimes the parameter t (time) is a vector rather than being a scalar. Why is that happening and how to fix it?

I am printing "t" in the middle of My_OutputFcn and here is a copy of the command window:

t =

           0    0.1500

t =

      0.0050

t =

      0.0100

t =

      0.0150

t =

      0.0200

t =

      0.0250

t =

      0.0300

t =

      0.0350

t =

      0.0400    0.0450

t =

      0.0500

t =

      0.0550    0.0600

Any help would be greatly appreciated.