Undefined Index Errors in class-eventbrite-api-widget.php

When I have debug mode turned on, I get two errors related to undefined index errors as is the following:

Notice: Undefined index: number in /home/flsidf5/public_html/wp-content/plugins/widget-for-eventbrite-api/includes/class-eventbrite-api-widget.php on line 162

Notice: Undefined index: order_by in /home/flsidf5/public_html/wp-content/plugins/widget-for-eventbrite-api/includes/class-eventbrite-api-widget.php on line 179

Seems to relate to these pieces of code:

$instance[‘number’] = (int) $new_instance[‘number’];

$instance[‘order_by’] = sanitize_text_field( $new_instance[‘order_by’] );

Any idea how to correct this?

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