If your electric range clock's LED is giving you odd number/letter combinations, it's because the Electronic Control Range has detected a problem that must be corrected. The number/letter combinations are known as error codes, which correspond to particular range/oven parts that need to be repaired or replaced.
Some range/oven parts will always register error codes when they go bad. Some models of range/ovens only display error codes for the clock and control panel itself and don't diagnose other problems. What's more, the error codes differ greatly from brand to brand.
You will need your owner manual to interpret the error codes for your unit. You may also need to search for further information on these codes as many manufacturers only intend the codes to be interpreted by trained professionals. It all depends on the model you own, and the range/oven replacement parts you need!