Help needed to define the array key for serialized data

I’m using YITH Point of Sale to manage a stock per store, and this plugin has two meta fields :

_yith_pos_multistock_enabled

This is a simple “yes” or “no”

_yith_pos_multistock

This is encoded as serialized data like a:2:{i:8924;i:7;i:9131;i:3;}, where :

• 8924 refers to the Store 1
• 7 refers to the stock of Store 1
• 9131 refers to the Store 2
• 3 refers to the stock of Store 2

Now, in your plugin, when you select “multiple values / serialized”, it asks for array keys but I’m facing difficulty to define this information. I tried entering “8924; 9131” or “8924,9131” but I’m not able to make it work. What am I supposed to enter exactly there?

Thanks