And what numbers are those?
Are these values in a field?
Are they an auto-entered serial number field?
Or something else?
Without more information about the design and intended function of your database, there are any number of possible reasons for what you report and very few of them involve there being a bug in the FileMaker Pro software.
Its a Serial number.
Find the attached screenshot the number 140252 and 140258 are missing.
There are any number of possible reasons that such would be the case.
a) The records may have been deleted by either a user or a script. Such a record deletion can also be part of a cascading delete if the delete option was specified in a relationship. In that case, deleting a record in a related table might delete records in this table.
b) The "next serial value" may have been reset to a larger value just before the records numbered 140253 and 140259 were created. (unlikely, but possible).
c) If at any point, the records in this file were imported from another file--such as when an update was deployed to to rescue data from a damaged file, either the record was not imported at that time or the field's next serial value was incorrectly updated after the import.
d) Since the records currently shown are unsorted, it is possible that the records are present but not in the expected location. Yes, auto-entered serial numbers should appear in the same order that you get when the records are unsorted but there are exceptions to that general rule. For example, see c) above. If the records were imported from another source, they may not have been imported in the expected order.
e) The records originally numbered with one of these missing values could still exist in the table, but a script or user might have modified the value of the serial number unless you've prohibited modification of this field.
f) Your file could be damaged or have been damaged at some point in the past. File Corruption can lead to the loss of data in your file.
I recommend that you first perform finds for records with the missing serial numbers if you have not already done so in order to make sure that the recors are truly missing. Then, run a recover on either this file or a very recent back up copy of the file just to check for possible file corruption. Whether damage is found or not, the final step is to check back up copies of your file for records with the missing serial numbers. If you can find the missing records in a back up copy of your file, you can import them into your current copy to restore the missing records. The date of the most recent back up copy found with the missing records might possibly provide a clue to help you figure out how this happened.