React Selector used with Grid type of UI

Code have selector written from below package & while rendering grid(looping the items) i am using selector to fetch the data & issue is each output is actually the output of first element in loop. Selector document mentions until input is not changes its memorized but exactly how to apply this is still unclear.

import { createSelector } from 'reselect';

Here is some more code snippet :

import { createSelector } from 'reselect';

export const _spreadSelector = createSelector(
  [_level2BuySelector, _level2SellSelector],
  (buy, sell) => {
    ........

    return new BigNumber(0);
  }
);

 Called by :

const spread = _spreadSelector (props.state,{selectedProductId: props.instruments[0].Product1});