If there is an infinity sign ∞ as your stock level for your variants, this indicates 'Manage Stock Level' was unchecked when creating the product on TradeGecko or the product has been imported from your Sales Channels as such. Shopify's equivalent setting to 'Manage Stock Levels' is 'Inventory Policy', while on On WooCommerce is 'Manage Stock'. If the setting for the product is disabled on the Sales Channel during import, 'Manage Stock Level' will be disabled on TradeGecko and will be reflected with an infinity sign.
You can update this setting in TradeGecko by going to your Products page > from the Bulk Manage drop-down menu> select Update Existing Products > Click on No, I need to download a list of my products > Select Manage Stock under Product Attributes. Click on Build Product Sheet and Download Product Sheet. To enable Manage Stock, set the Value to TRUE under the 'Manage Stock' column or FALSE to disable. Save and re-upload the CSV file.