Kindly advise if your were able to complete the packing?
I know this is your 1st time using this box and unsure about the shipping.
However I can assure you that it will be ok to ship the merchandise in this box even when it is heavier than the indicated 25 Kgs.
As long as all the merchandise fits in there it is ok and as long as it does not exceed 68 Kgs.
I have attached a sample airwaybill copy on how this should be completed with the weight indication also.
If it puts you at ease you could tape the bottom of the box also with duct tape or clear tape, whichever you have in stock or you could request the courier to tape it for you.
They should have clear tape on them.
Kindly let me know if additional information is required.
It is a pleasure doing business with you.