I have not had this problem with this tool, but have had others. Not a reliable tool IMO You can find a simple table on line and print it out.
Hi there. Most alkaline batteries are at risk of leaking, it is recommended that batteries are removed from the device if it will not be used for several months. There are alkaline batteries on the market that are guaranteed not to leak which may be worth looking into. For further assistance, contact us at 1-877-BOSCH99 (1-877-267-2499) from Mon-Fri 7A-7P CST.
You can't calibrate it, IMO throw it away and get a stabila