Just add the following code in your functions.php file of your child theme to change the default word count in the excerpts,

function custom_excerpt_length( $length ) {
	return 20; //chnge this to number of words you want in your excerpt
add_filter( 'imd_excerpt_word_count', 'custom_excerpt_length', 999 );

Change the number ’20’ to the number of words you want in your excerpt.

iMedica be default does not break excerpt until the sentence is complete but this in some cases shows an uneven number of word count in the excerpt.

To change this behavior you can add this code –

 * Control if excerpt should consider full sentence or not.
 * iMedica excerpts by default do not break the work before sentense is completed.
 * @return (boolean) false: break excerpt before sentence ends. | true: do not break excerpt before sentence is complete
 * @since iMedica 3.1.3
function excerpt_complete_sentence() {
	return false;
add_filter( 'imedica_excerpt_till_sentence_ends', 'excerpt_complete_sentence' );